Systems and methods of protecting wireless power receivers using multiple rectifiers and establishing in-band communications using multiple rectifiers

ABSTRACT

A wireless-power receiver includes an antenna coupled to a rectifier, and a depletion-mode switch coupled to the rectifier. The depletion-mode switch can create an impedance mismatch or an impedance match between the rectifier and the antenna. While the depletion-mode switch is in a default-closed state, it creates an impedance mismatch between the rectifier and the antenna. A first amount of alternating current received by the antenna as radio frequency (RF) signals is reflected away from the rectifier&#39;s input due to the impedance mismatch. A second amount of the alternating current causes the depletion-mode switch to begin transitioning to an open state, creating an impedance match between the rectifier and the antenna. While the depletion-mode switch is in the open state, creating an impedance match between the rectifier and the antenna, alternating current received by the antenna flows through the rectifier&#39;s input to be converted into direct current.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 62/907,234, filed Sep. 27, 2019, and to U.S. Provisional Application Ser. No. 62/903,675, filed Sep. 20, 2019. Each of these applications is hereby incorporated by reference.

TECHNICAL FIELD

The embodiments herein generally relate to antennas, software, and devices used in wireless power transmission systems and, more specifically, to systems and methods of receivers with rectifiers capable of being used for communicating, warning of power fluctuations, and protecting against power surges.

BACKGROUND

Conventional wireless power transmission systems, such as charging pads, utilize both RF signals and induction to generate a magnetic field that is used to charge a device. These charging pads (i.e., transmitters) have to communicate with receivers to ensure that the device to be charge is not damaged by an unexpected surge in power or a power loss. To overcome such issues, the current approach has been to add a wireless communication chip (e.g., a Bluetooth radio) to both the transmitter and the receiver, which allows the devices to communicate with each other. However, the addition on these communication chips can be costly, which increases the cost of the wireless power transmission systems. In addition, in electronic devices where space is at a premium, the wireless communication chips occupy valuable shape.

Furthermore, establishing a communication connection between the transmitter and the receiver takes time, which can slow the time to start sending power from the transmitter to a receiver. Such a result is undesirable, because the wireless transmission of power is intended to be less involved than plugging in a device into a power source.

SUMMARY

Accordingly, there is a need for wireless charging systems (e.g., radio frequency (RF) charging pads) that address the problems identified above. To this end, systems and methods are described herein that are capable of allowing receivers to communicate and prepare for changes in power without having a dedicated communication chip (e.g., a Bluetooth radio). In some embodiments, such system and methods use to two rectifiers to solve the identified problems. It is also understood that in a two rectifier embodiment, a first rectifier is used to convert RF power to useable direct current (DC) to charge an electronic device while a second rectifier is configured to receive a smaller portion of power than the first rectifier, whereby this smaller portion of power is not used to charge the electronic device.

Typically, outputs of rectifiers are coupled to capacitors capable of reducing ripple. These capacitors are sized to match the outputted direct current, and the larger the direct current, the larger the capacitor needs to be to reduce ripple. However, these capacitors delay the detection (by either not charging or discharging fast enough) in incoming power. As a result, a second smaller rectifier that receives a smaller portion of power is capable of detecting changes in power faster than the components coupled to the first (i.e., larger power handling) rectifier. And once the second (i.e. smaller power handling) rectifier detects the change in power, it can communicate with the components coupled to the output of the first rectifier, and warn them that a power change has occurred.

In another aspect, this two rectifier embodiment allows for the second rectifier to adjust the impedance of the receiver causing a portion of the received RF power to be reflected back to the wireless power transmitter. By adjusting this impedance, the wireless power receiver can communicate with the wireless power transmitter. In one example, the wireless power transmitter can modulate its impedance (e.g., through control of the second rectifier) to signal the wireless power transmitter that a reduction in power is required by the wireless power receiver, or simply that power is no longer required.

(A1) In some embodiments, the solution explained above can be implemented on a wireless power receiver that includes a wireless-power-receiving antenna configured to receive radio frequency (RF) power signals, and convert energy from the received RF signals into an alternating current. The wireless power receiver also includes a primary rectifier that is configured to: (i) receive a first portion of the alternating current, and (ii) rectify the first portion of the alternating current into primary direct current having a first power level, the primary direct current used to provide power or charge to an electronic device. The wireless power receiver also includes a secondary rectifier that is configured to: (i) receive a second portion of the alternating current, and (ii) rectify the second portion of the alternating current into a secondary direct current having a second power level. The second power level of the secondary direct current is less than the first power level of the primary direct current. While a first voltage associated with the primary direct current and a second voltage associated with the secondary direct current can be similar, the power levels (the first and second power levels above) differ because load resistances for the primary and secondary direct currents are different.

(A2) In some embodiments of A1, the second power level of the secondary direct current indicates whether the antenna is receiving RF signals from a wireless-power-transmitting device.

(A3) In some embodiments of A2, an RF coupler is coupled to the antenna, and the RF coupler includes distinct first and second outputs. Furthermore, the primary rectifier is coupled to the first output of the RF coupler and the secondary rectifier is coupled to the second output of the RF coupler.

(A4) In some embodiments of A3, at least one impedance matching network is positioned between and coupled to the first output of the RF coupler and the secondary rectifier, whereby the at least one matching network is configured to match an impedance of a source of the RF signals.

(A5) In some embodiments of A3, at least one impedance matching network is positioned between and coupled to an input of the RF coupler and the antenna, whereby the at least one matching network is configured to match an impedance of a source of the RF signals.

(A6) In some embodiments of A3, the wireless power receiver also includes (i) one or more additional electrical components that are used to deliver the primary direct current that is used to power or charge to the electronic device and (ii) a controller configured to: (a) detect that the second power level of the secondary direct current satisfies one or more power-detection thresholds that indicate that the antenna is receiving RF signals from a wireless-power-transmitting device and (b) in response to detecting that the second direct current satisfies the one or more power-detection thresholds, send a signal that causes each of the one or more additional electrical components to prepare for receiving the primary direct current.

(A7) In some embodiments of A6, the one or more power-detection thresholds are satisfied when a voltage of the secondary direct current is in a range of approximately 5 volts to 30 volts. In some circumstances, the range can be either broadened (e.g., to be 1 volts to 40 volts), or narrowed (e.g., to be 5 volts to 10 volts).

(A8) In some embodiments of A7, detecting that the second power level of the secondary direct current satisfies one or more power-detection thresholds is performed by comparing the second power level to a respective power-detection threshold of the one or more power-detection thresholds at a first measurement point, a second measurement point, or both the first and second measurement points.

(A9) In some embodiments of A8, the first measurement point is located before a voltage divider that is configured to step down the voltage of the secondary direct current, and the second measurement point is located after the voltage divider.

(A10) In some embodiments of A6, the second portion of the alternating current is approximately less than 1% of the alternating current. In some embodiments, having the alternating current less than 1% minimizes impact on overall RF to DC conversion efficiency.

(A11) In some embodiments of A6, the wireless power receiver also includes: (i) a first storage component and (ii) a second storage component having a lower storage capacity that is less than the first storage component. Furthermore, the first storage component is coupled to an output of the primary rectifier while the second storage component is coupled to an output of the secondary rectifier. Moreover, the second storage component, due to its lower storage capacity, is configured to discharge faster than the first storage component, whereby discharge of the second storage component indicates to the wireless power receiver that RF signals are no longer being received at the antenna.

(A12) In some embodiments of any of A1-A11, the secondary rectifier is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode, and (iii) a second diode. The input of the secondary rectifier is coupled to: a cathode of a first diode, wherein an anode of the first diode is coupled to a ground; and an anode of a second diode, wherein a cathode of the second diode is coupled to an output of the secondary rectifier.

(A13) In some embodiments of any of A1-A12, the secondary rectifier is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode-connected transistor, and (iii) a second diode-connected transistor. The input of the secondary rectifier is coupled to: (i) a first diode-connected transistor, wherein the first diode-connected transistor is connected to a ground; and (ii) a second diode-connected transistor, wherein the second diode-connected transistor is connected to an output of the secondary rectifier.

(A14) In some embodiments of any of A3-A13, the RF coupler is a directional coupler.

(A15) In some embodiments of any of A3-A13, the RF coupler is a capacitive coupler.

(A16) In some embodiments of any of A3-A13, the RF coupler is a resistive coupler.

(B1) In another aspect, a method of communication between a wireless power receiver to a wireless power transmitter is performed. In some embodiments, the method includes receiving, by an antenna of the wireless power receiver, radio frequency (RF) signals from the wireless power transmitter, whereby the wireless power receiver substantially matches an impedance of the wireless power transmitter. The method also includes, while receiving the RF signals from the wireless power transmitter: (i) determining whether a communication criterion is satisfied, and (ii) in accordance with a determination that the communication criterion is satisfied, introducing an impedance mismatch between the wireless power receiver and the wireless power transmitter that causes a portion of the RF signals to be reflected by the antenna as a modulated signal. The transmitter is configured to receive and interpret the modulated signal without using a separate communication radio.

(B2) In some embodiments of B1, introducing the impedance mismatch includes creating one or more impedance mismatches between the wireless power receiver and the wireless power transmitter interspersed with one or more impedance matches between the wireless power receiver and the wireless power transmitter forming the modulated signal.

(B3) In some embodiments of B2, the wireless power transmitter interprets the modulated signal as an instruction to cease sending the RF signals to the wireless power receiver.

(B4) In some embodiments of B2, the wireless power transmitter interprets the modulated signal as an instruction to adjust transmission characteristics of the RF signals to the wireless power receiver.

(B5) In some embodiments of any of B1-B4, the method further includes, after introducing the impedance mismatch and while continuing to receive the RF signals from the wireless power transmitter, matching the impedance between the wireless power receiver and the wireless power transmitter, which stops reflection of the portion of the RF signals by the antenna.

(B6) In some embodiments of any of B1-B5, the wireless power transmitter ceases to transmit the RF signals to the wireless power receiver in response to receiving the modulated signal.

(B7) In some embodiments of any of B1-B6, the wireless power receiver includes an auxiliary rectifier, coupled to the antenna that receives some of the RF signals. Furthermore, introducing the impedance mismatch between the wireless power receiver and the wireless power transmitter includes adjusting a load of the auxiliary rectifier.

(B8) In some embodiments of B7, the wireless power receiver includes an auxiliary matching network coupled to and positioned between the antenna and the auxiliary rectifier. Furthermore, adjusting the load of the auxiliary rectifier causes an impedance mismatch between the auxiliary matching network of the wireless power receiver and the wireless power transmitter, which results the portion of the RF signals being reflected by the antenna.

(B9) In some embodiments of B7, the wireless power receiver includes a switch coupled to a load-adjusting mechanism, and the load-adjusting mechanism is coupled to the auxiliary rectifier. Moreover, the toggling the switch, which causes a change within the load-adjusting mechanism that produces a change in the load of the receiver, which results in the impedance mismatch between the wireless power receiver and the wireless power transmitter.

(B10) In another aspect, a wireless power receiver (e.g., receiver 120, FIG. 3) is provided. In some embodiments, the wireless power receiver includes: an antenna, a rectifier coupled to the antenna, a switch coupled to the rectifier, the switch being configured to create an impedance mismatch or match before an input of the rectifier, one or more processors; and memory storing one or more programs, which when executed by the one or more processors cause the transmitter to perform the method described in any one of B1-B9.

(B11) In yet another aspect, a wireless power receiver is provided and the wireless power receiver (e.g., receiver 120, FIG. 3) includes means for performing the method described in any one of B1-B9.

(B12) In still another aspect, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium stores executable instructions that, when executed by the wireless power receiver with one or more processors/cores, cause the wireless power receiver to perform the method described in any one of B1-B9.

(C1) In yet another aspect, a method of power surge protection for a wireless power receiver is performed. In some embodiments, this method is performed at a wireless power receiver that includes: (i) an antenna, (ii) a rectifier coupled to the antenna, and (iii) a switch coupled to the rectifier, the switch configured to create an impedance mismatch or match before an input of the rectifier. Further, the method includes, while the switch is in a default-closed state that grounds the switch and creates an impedance mismatch before an input of the rectifier: (i) receiving, by the antenna of the wireless power receiver, radio frequency (RF) signals as an alternating current, whereby a first portion of the alternating current is reflected away from the input of the rectifier due to the impedance mismatch between the wireless power receiver and the wireless power transmitter, and a second portion of the alternating current flows through the switch and to ground, and (ii) while the switch is in an open state that creates an impedance match between the wireless power receiver and the wireless power transmitter at the input of the rectifier: the first portion of the alternating current flows through the input of the rectifier, allowing the first portion of the alternating current to be converted into direct current that is used to charge or power a wireless electronic device. Moreover, the second portion of the alternating current flows through the switch and to the input of the rectifier, allowing the second portion of the alternating current to be converted into direct current that is used to charge or power a wireless electronic device.

(C2) In some embodiments of C1, a negative voltage generator is placed to drive the switch. For example, the negative voltage generator may be placed before the switch to drive the switch.

(C3) In some embodiments of any of C1-C2, the switch transitions from the default-closed state to the open state gradually over a period of time, and during the period of time, a part of the first portion of the alternating current continues to be reflected away from the input of the rectifier.

(C4) In some embodiments of C3, the switch transitions from default-closed to open state by using a Gallium Nitride (GaN) switch or a depletion mode metal oxide semiconductor (MOS) switch.

(C5) In some embodiments of C3, the method also includes, dynamically adjusting the period of time based on a detected voltage of the alternating current.

(C6) In some embodiments of C5, dynamically adjusting includes reducing the period of time based on a determination that the detected voltage does not satisfy a defined threshold value.

(C7) In some embodiments of C5, dynamically adjusting includes increasing the period of time based on a determination that the detected voltage satisfies a defined threshold value.

(C8) In some embodiments of any of C1-C7, the switch has a voltage threshold that is met before it enters the open fully open.

(C9) In some embodiments of C8, the voltage threshold is zero volts.

(C10) In some embodiments of any of C1-C9, the method further includes, while the switch is in the open state, ceasing to receive the RF signals by the antenna of the wireless power receiver. Ceasing to receive the RF signals causes the switch to transition back to the default-closed state from the open state.

(C11) In some embodiments of any of C1-C10, the wireless power receiver includes a coupling mechanism that is coupled to the antenna, the coupling mechanism including a first output and a second output. The first output of the coupling mechanism is coupled to the rectifier and the second output of the coupling mechanism is coupled to the switch.

(C12) In some embodiments of C11, the coupling mechanism partitions the alternating current. Further, the coupling mechanism: (i) directs a first portion of the alternating current to the first output of the coupling mechanism and (ii) directs a second portion of the alternating current to the second output of the coupling mechanism.

(C13) In some embodiments of C1-C12, the switch is coupled to an output of the rectifier.

(C14) In some embodiments of C1-C12, wherein the wireless power receiver also includes a matching network having (i) an input coupled to the first output of the coupling mechanism and (ii) an output coupled to the rectifier.

(C15) In some embodiments of C14, the switch is coupled to the matching network and the rectifier.

(C16) In another aspect, a wireless power receiver (e.g., receiver 120, FIG. 3) is provided. In some embodiments, the wireless power receiver includes: an antenna, a rectifier coupled to the antenna, a switch coupled to the rectifier, the switch being configured to create an impedance mismatch or match before an input of the rectifier, one or more processors; and memory storing one or more programs, which when executed by the one or more processors cause the transmitter to perform the method described in any one of C1-C15.

(C17) In yet another aspect, a wireless power receiver is provided and the receiver (e.g., receiver 120, FIG. 3) includes means for performing the method described in any one of C1-C15.

(C18) In still another aspect, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium stores executable instructions that, when executed by the wireless power receiver with one or more processors/cores, cause the wireless power receiver to perform the method described in any one of C1-C15.

Note that the various embodiments described above can be combined with any other embodiments described herein. The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not intended to circumscribe or limit the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present disclosure can be understood in greater detail, a more particular description may be had by reference to the features of various embodiments, some of which are illustrated in the appended drawings. The appended drawings, however, merely illustrate pertinent features of the present disclosure and are therefore not to be considered limiting, for the description may admit to other effective features.

FIG. 1A is a block diagram of an RF wireless power transmission system, in accordance with some embodiments.

FIG. 1B is another block diagram of an RF wireless power transmission system, in accordance with some embodiments.

FIG. 1C is a block diagram showing components of an example RF charging pad that includes an RF power transmitter integrated circuit and antenna zones, in accordance with some embodiments.

FIG. 1D is a block diagram showing components of an example RF charging pad that includes an RF power transmitter integrated circuit coupled to a switch, in accordance with some embodiments.

FIG. 2 is a block diagram showing components of an example RF transmitter, in accordance with some embodiments.

FIG. 3 is a block diagram showing components of an example RF receiver, in accordance with some embodiments.

FIG. 4A is a circuit schematic illustrating an example RF receiver with two rectifiers for detecting changes in received RF power, in accordance with some embodiments.

FIG. 4B is a circuit schematic illustrating points at which a coupling mechanism may be added to the circuit, in accordance with some embodiments.

FIG. 4C illustrates circuit schematics for exemplary coupling mechanisms, in accordance with some embodiments, in accordance with some embodiments.

FIG. 4D illustrates circuit schematics for exemplary rectifiers, in accordance with some embodiments, in accordance with some embodiments.

FIG. 4E illustrates a circuit schematics for detecting when RF power is no longer received at the antenna, in accordance with some embodiments.

FIG. 4F illustrates circuit schematics of simplified rectifiers, in accordance with some embodiments.

FIG. 5A depicts a circuit schematic illustrating a system for protecting sensitive electrical components from power surges, in accordance with some embodiments.

FIG. 5B depicts a circuit schematic illustrating points at which a coupling mechanism may be added to the circuit, in accordance with some embodiments.

FIG. 6A depicts a circuit schematic illustrating a receiver capable of communicating with a transmitter, in accordance with some embodiments.

FIG. 6B depicts a circuit schematic illustrating points at which a coupling mechanism may be added to the circuit, in accordance with some embodiments.

FIG. 6C illustrates is a circuit schematic illustrating exemplary components for adjusting the load of a rectifier to cause an impedance mismatch, in accordance with some embodiments.

FIG. 7 is a flow diagram showing a process of a receiver communicating with a transmitter, in accordance with some embodiments.

In accordance with common practice, the various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may not depict all of the components of a given system, method or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

FIG. 1A is a block diagram of components of wireless power transmission environment 100, in accordance with some embodiments. Wireless power transmission environment 100 includes, for example, transmitters 102 (e.g., transmitters 102 a, 102 b . . . 102 n) and one or more receivers 120 (e.g., receivers 120 a, 120 b . . . 120 n). In some embodiments, each respective wireless power transmission environment 100 includes a number of receivers 120, each of which is associated with a respective electronic device 122. In some instances, the transmitter 102 is referred to herein as a “wireless-power-transmitting device” or a “wireless power transmitter.” Additionally, in some instances, the receiver 120 is referred to herein as a “wireless-power-receiving device” or a “wireless power receiver.”

An example transmitter 102 (e.g., transmitter 102 a) includes, for example, one or more processor(s) 104, a memory 106, one or more antenna arrays 110, one or more communications components 112 (also referred to herein as a “wireless communications radio,” a “communications radio” or simply a “radio”), and/or one or more transmitter sensors 114. In some embodiments, these components are interconnected by way of a communications bus 107. References to these components of transmitters 102 cover embodiments in which one or more of these components (and combinations thereof) are included. The components are discussed in further detail below with reference to FIG. 2.

In some embodiments, a single processor 104 (e.g., processor 104 of transmitter 102 a) executes software modules for controlling multiple transmitters 102 (e.g., transmitters 102 b . . . 102 n). In some embodiments, a single transmitter 102 (e.g., transmitter 102 a) includes multiple processors 104, such as one or more transmitter processors (configured to, e.g., control transmission of signals 116 by antenna array 110), one or more communications component processors (configured to, e.g., control communications transmitted by communications component 112 and/or receive communications by way of communications component 112) and/or one or more sensor processors (configured to, e.g., control operation of transmitter sensor 114 and/or receive output from transmitter sensor 114).

The wireless power receiver 120 receives power transmission signals 116 and/or communication signals 118 transmitted by transmitters 102. In some embodiments, the receiver 120 includes one or more antennas 124 (e.g., an antenna array including multiple antenna elements), power converter 126, receiver sensor 128, and/or other components or circuitry (e.g., processor(s) 140, memory 142, and/or communication component(s) 144. In some embodiments, these components are interconnected by way of a communications bus 146. References to these components of receiver 120 cover embodiments in which one or more of these components (and combinations thereof) are included.

The receiver 120 converts energy from received signals 116 (also referred to herein as RF power transmission signals, or simply, RF signals, RF waves, power waves, or power transmission signals) into electrical energy to power and/or charge electronic device 122. For example, the receiver 120 uses the power converter 126 to convert energy derived from power waves 116 to alternating current (AC) electricity or direct current (DC) electricity to power and/or charge the electronic device 122. Non-limiting examples of the power converter 126 include rectifiers, rectifying circuits, voltage conditioners, among suitable circuitry and devices.

In some embodiments, the receiver 120 is a standalone device that is detachably coupled to one or more electronic devices 122. For example, the electronic device 122 has processor(s) 132 for controlling one or more functions of the electronic device 122, and the receiver 120 has processor(s) 140 for controlling one or more functions of the receiver 120.

In some embodiments, the receiver 120 is a component of the electronic device 122. For example, processors 132 control functions of the electronic device 122 and the receiver 120. In addition, in some embodiments, the receiver 120 includes one or more processors 140, which communicates with processors 132 of the electronic device 122.

In some embodiments, the electronic device 122 includes one or more processors 132, memory 134, one or more communication components 136, and/or one or more batteries 130. In some embodiments, these components are interconnected by way of a communications bus 138. In some embodiments, communications between electronic device 122 and receiver 120 occur via communications component(s) 136 and/or 144. In some embodiments, communications between the electronic device 122 and the receiver 120 occur via a wired connection between communications bus 138 and communications bus 146. In some embodiments, the electronic device 122 and the receiver 120 share a single communications bus.

In some embodiments, the receiver 120 receives one or more power waves 116 directly from the transmitter 102 (e.g., via one or more antennas 124). In some embodiments, the receiver 120 harvests power waves from one or more pockets of energy created by one or more power waves 116 transmitted by the transmitter 102. In some embodiments, the transmitter 102 is a near-field transmitter that transmits the one or more power waves 116 within a near-field distance (e.g., less than approximately six inches away from the transmitter 102). In other embodiments, the transmitter 102 is a far-field transmitter that transmits the one or more power waves 116 within a far-field distance (e.g., more than approximately six inches away from the transmitter 102).

After the power waves 116 are received and/or energy is harvested from them, circuitry (e.g., integrated circuits, amplifiers, rectifiers, and/or voltage conditioner) of the receiver 120 converts the energy of the power waves to usable power (i.e., electricity), which powers the electronic device 122 and/or is stored to battery 130 of the electronic device 122. In some embodiments, a rectifying circuit of the receiver 120 translates the electrical energy from AC to DC for use by the electronic device 122. In some embodiments, a voltage conditioning circuit increases or decreases the voltage of the electrical energy as required by the electronic device 122. In some embodiments, an electrical relay conveys electrical energy from the receiver 120 to the electronic device 122.

In some embodiments, the electronic device 122 obtains power from multiple transmitters 102 and/or using multiple receivers 120. In some embodiments, the wireless power transmission environment 100 includes a plurality of electronic devices 122, each having at least one respective receiver 120 that is used to harvest power waves from the transmitters 102 into power for charging the electronic devices 122.

In some embodiments, the one or more transmitters 102 adjust values of one or more characteristics (e.g., waveform characteristics, such as phase, gain, direction, amplitude, polarization, and/or frequency) of power waves 116. For example, a transmitter 102 selects a subset of one or more antenna elements of antenna array 110 to initiate transmission of power waves 116, cease transmission of power waves 116, and/or adjust values of one or more characteristics used to transmit power waves 116. In some embodiments, the one or more transmitters 102 adjust power waves 116 such that trajectories of power waves 116 converge at a predetermined location within a transmission field (e.g., a location or region in space), resulting in controlled constructive or destructive interference patterns. The transmitter 102 may adjust values of one or more characteristics for transmitting the power waves 116 to account for changes at the wireless power receiver that may negatively impact transmission of the power waves 116.

Note that, in some embodiments, the transmitter 102 utilizes beamforming techniques to wirelessly transfer power to a receiver 120, while in other embodiments, the transmitter 102 does not utilize beamforming techniques to wirelessly transfer power to a receiver 120 (e.g., in circumstances in which no beamforming techniques are used, the transmitter controller IC 160 discussed below might be designed without any circuitry to allow for use of beamforming techniques, or that circuitry may be present, but might be deactivated to eliminate any beamforming control capability).

In some embodiments, respective antenna arrays 110 of the one or more transmitters 102 may include a set of one or more antennas configured to transmit the power waves 116 into respective transmission fields of the one or more transmitters 102. Integrated circuits (FIG. 1C) of the respective transmitter 102, such as a controller circuit (e.g., a radio frequency integrated circuit (RFIC)) and/or waveform generator, may control the behavior of the antennas. For example, based on the information received from the receiver 120 by way of the communication signal 118, a controller circuit (e.g., processor 104 of the transmitter 102, FIG. 1A) may determine values of the waveform characteristics (e.g., amplitude, frequency, trajectory, direction, phase, polarization, among other characteristics) of power waves 116 that would effectively provide power to the receiver 120, and in turn, the electronic device 122. The controller circuit may also identify a subset of antennas from the antenna arrays 110 that would be effective in transmitting the power waves 116. In some embodiments, a waveform generator circuit (not shown in FIG. 1A) of the respective transmitter 102 coupled to the processor 104 may convert energy and generate the power waves 116 having the specific values for the waveform characteristics identified by the processor 104/controller circuit, and then provide the power waves to the antenna arrays 110 for transmission.

In some embodiments, the communications component 112 transmits communication signals 118 by way of a wired and/or wireless communication connection to the receiver 120. In some embodiments, the communications component 112 generates communication signals 118 used for triangulation of the receiver 120 (e.g., test signals). In some embodiments, the communication signals 118 are used to convey information between the transmitter 102 and receiver 120 for adjusting values of one or more waveform characteristics used to transmit the power waves 116 (e.g., convey amounts of power derived from RF test signals). In some embodiments, the communication signals 118 include information related to status, efficiency, user data, power consumption, billing, geo-location, and other types of information.

In some embodiments, the communications component 112 transmits communication signals 118 to the receiver 120 by way of the electronic device 122 a. For example, the communications component 112 may convey information to the communications component 136 of the electronic device 122 a, which the electronic device 122 a may in turn convey to the receiver 120 (e.g., via bus 138).

In some embodiments, the communications component 112 includes a communications component antenna for communicating with the receiver 120 and/or other transmitters 102 (e.g., transmitters 102 b through 102 n). In some embodiments, these communication signals 118 are sent using a first channel (e.g., a first frequency band) that is independent and distinct from a second channel (e.g., a second frequency band distinct from the first frequency band) used for transmission of the power waves 116.

In some embodiments, the receiver 120 includes a receiver-side communications component 144 configured to communicate various types of data with one or more of the transmitters 102, through a respective communication signal 118 generated by the receiver-side communications component (in some embodiments, a respective communication signal 118 is referred to as an advertising signal). The data may include location indicators for the receiver 120 and/or electronic device 122, a power status of the device 122, status information for the receiver 120, status information for the electronic device 122, status information about the power waves 116, and/or status information for pockets of energy. In other words, the receiver 120 may provide data to the transmitter 102, by way of the communication signal 118, regarding the current operation of the system 100, including: information identifying a present location of the receiver 120 or the device 122, an amount of energy (i.e., usable power) received by the receiver 120, and an amount of power received and/or used by the electronic device 122, among other possible data points containing other types of information.

In some embodiments, the data contained within communication signals 118 is used by the electronic device 122, the receiver 120, and/or the transmitters 102 for determining adjustments to values of one or more waveform characteristics used by the antenna array 110 to transmit the power waves 116. Using a communication signal 118, the transmitter 102 communicates data that is used, e.g., to identify receivers 120 within a transmission field, identify electronic devices 122, determine safe and effective waveform characteristics for power waves, and/or hone the placement of pockets of energy. In some embodiments, the receiver 120 uses a communication signal 118 to communicate data for, e.g., alerting transmitters 102 that the receiver 120 has entered or is about to enter a transmission field(e.g., come within wireless-power-transmission range of a transmitter 102), provide information about the electronic device 122, provide user information that corresponds to the electronic device 122, indicate the effectiveness of received power waves 116, and/or provide updated characteristics or transmission parameters that the one or more transmitters 102 use to adjust transmission of the power waves 116.

In some embodiments, the receiver 120 does not include a distinct communications component 144. Rather, the receiver 120 is configured to reflect RF signals transmitted by the transmitter 102 at the one or more antennas 124 and, importantly, modulate the reflected RF signals to convey data (or a message) to transmitter 102. In such embodiments, the transmitter 102 may also lack a distinct communications component. Instead, the transmitter 102 may receive the reflected RF signals at the one or more antenna arrays 110, and the transmitter 102 may demodulate the reflected RF signals in order to interpret them. Reflecting RF signals by the receiver 120 is discussed in further detail below with reference to FIGS. 6A-6C.

In some embodiments, transmitter sensor 114 and/or receiver sensor 128 detect and/or identify conditions of the electronic device 122, the receiver 120, the transmitter 102, and/or a transmission field. In some embodiments, data generated by the transmitter sensor 114 and/or receiver sensor 128 is used by the transmitter 102 to determine appropriate adjustments to values of one or more waveform characteristics used to transmit the power waves 116. Data from transmitter sensor 114 and/or receiver sensor 128 received by the transmitter 102 includes, e.g., raw sensor data and/or sensor data processed by a processor 104, such as a sensor processor. Processed sensor data includes, e.g., determinations based upon sensor data output. In some embodiments, sensor data received from sensors that are external to the receiver 120 and the transmitters 102 is also used (such as thermal imaging data, information from optical sensors, and others).

FIG. 1B is another block diagram of an RF wireless power transmission system 150 in accordance with some embodiments. In some embodiments, the RF wireless power transmission system 150 includes a far-field transmitter (not shown). In some embodiments, the RF wireless power transmission system 150 includes a RF charging pad 151 (also referred to herein as a near-field (NF) charging pad 151 or RF charging pad 151). The RF charging pad 151 may be an example of the transmitter 102 in FIG. 1A.

In some embodiments, the RF charging pad 151 includes an RF power transmitter integrated circuit 160 (described in more detail below). In some embodiments, the RF charging pad 151 includes one or more optional communications components 112 (e.g., wireless communication components, such as WI-FI or BLUETOOTH radios). Alternatively, in some embodiments, the RF charging pad 151 does not include the optional communications components 112. In such embodiments, the RF charging pad 151 includes alternative means for communicating with other devices (e.g., the RF charging pad 151 receives and interprets RF signals reflected by a receiver 120). In some embodiments, the RF charging pad 151 also connects to one or more power amplifier units 108-1, . . . 108-n (PA or PA units) to control operation of the one or more power amplifier units when they drive external power-transfer elements (e.g., antennas 290). In some embodiments, RF power is controlled and modulated at the RF charging pad 151 via switch circuitry as to enable the RF wireless power transmission system to send RF power to one or more wireless receiving devices via the TX antenna array 110.

The optional communication component(s) 112 enable communication between the RF charging pad 151 and one or more communication networks, and are discussed in further detail above with reference to FIG. 1A. In some instances, the communication component(s) 112 are not able to communicate with wireless power receivers for various reasons, e.g., because there is no power available for the communication component(s) to use for the transmission of data signals or because the wireless power receiver 120 itself does not actually include any communication component of its own. As such, it is important to design near-field charging pads that are still able to uniquely identify different types of devices and, when a wireless power receiver is detected, figure out if that wireless power receiver is authorized to receive wireless power.

FIG. 1C is a block diagram of the RF power transmitter integrated circuit 160 (the “integrated circuit”) in accordance with some embodiments. In some embodiments, the integrated circuit 160 includes a CPU subsystem 170, an external device control interface, an RF subsection for DC to RF power conversion, and analog and digital control interfaces interconnected via an interconnection component, such as a bus or interconnection fabric block 171. In some embodiments, the CPU subsystem 170 includes a microprocessor unit (CPU) 202 with related Read-Only-Memory (ROM) 172 for device program booting via a digital control interface, e.g. an I²C port, to an external FLASH containing the CPU executable code to be loaded into the CPU Subsystem Random Access Memory (RAM) 174 (e.g., memory 206, FIG. 2A) or executed directly from FLASH. In some embodiments, the CPU subsystem 170 also includes an encryption module or block 176 to authenticate and secure communication exchanges with external devices, such as wireless power receivers that attempt to receive wirelessly delivered power from the RF charging pad 150.

In some embodiments, the RF IC 160 also includes (or is in communication with) a power amplifier controller IC 161A (PA IC) that is responsible for controlling and managing operations of a power amplifier (or multiple power amplifiers), including for reading measurements of impedance at various measurement points within the power amplifier 108, whereby these measurements are used, in some instances, for detecting of foreign objects. The PA IC 161A may be on the same integrated circuit at the RF IC 160, or may be on its on integrated circuit that is separate from (but still in communication with) the RF IC 160. Additional details regarding the architecture and operation of the PA IC are provided in U.S. Provisional Application No. 62/903,677, the disclosure of which is incorporated by reference herein in its entirety.

In some embodiments, executable instructions running on the CPU (such as those shown in the memory 106 in FIG. 2 and described below) are used to manage operation of the RF charging pad 151 and to control external devices through a control interface, e.g., SPI control interface 175, and the other analog and digital interfaces included in the RF power transmitter integrated circuit 160. In some embodiments, the CPU subsystem also manages operation of the RF subsection of the RF power transmitter integrated circuit 160, which includes an RF local oscillator (LO) 177 and an RF transmitter (TX) 178. In some embodiments, the RF LO 177 is adjusted based on instructions from the CPU subsystem 170 and is thereby set to different desired frequencies of operation, while the RF TX converts, amplifies, modulates the RF output as desired to generate a viable RF power level.

In the descriptions that follow, various references are made to antenna zones and power-transfer zones, which terms are used synonymously in this disclosure. In some embodiments the antenna/power-transfer zones may include antenna elements that transmit propagating radio frequency waves but, in other embodiments, the antenna/power transfer zones may instead include capacitive charging couplers that convey electrical signals but do not send propagating radio frequency waves.

In some embodiments, the RF power transmitter integrated circuit 160 provides the viable RF power level (e.g., via the RF TX 178) to an optional beamforming integrated circuit (IC) 109, which then provides phase-shifted signals to one or more power amplifiers 108. In some embodiments, the beamforming IC 109 is used to ensure that power transmission signals sent using two or more antennas 210 (e.g., each antenna 210 may be associated with a different antenna zone 290 or may each belong to a single antenna zone 290) to a particular wireless power receiver are transmitted with appropriate characteristics (e.g., phases) to ensure that power transmitted to the particular wireless power receiver is maximized (e.g., the power transmission signals arrive in phase at the particular wireless power receiver). In some embodiments, the beamforming IC 109 forms part of the RF power transmitter IC 160. In embodiments in which capacitive couplers (e.g., capacitive charging couplers 244) are used as the antennas 210, then optional beamforming IC 109 may not be included in the RF power transmitter integrated circuit 160.

In some embodiments, the RF power transmitter integrated circuit 160 provides the viable RF power level (e.g., via the RF TX 178) directly to the one or more power amplifiers 108 and does not use the beamforming IC 109 (or bypasses the beamforming IC if phase-shifting is not required, such as when only a single antenna 210 is used to transmit power transmission signals to a wireless power receiver). In some embodiments, the PA IC 161A receives the viable RF power level and provides that to the one or more power amplifiers 108.

In some embodiments, the one or more power amplifiers 108 then provide RF signals to the antenna zones 290 (also referred to herein as “power-transfer zones”) for transmission to wireless power receivers that are authorized to receive wirelessly delivered power from the RF charging pad 151. In some embodiments, each antenna zone 290 is coupled with a respective PA 108 (e.g., antenna zone 290-1 is coupled with PA 108-1 and antenna zone 290-N is coupled with PA 108-N). In some embodiments, multiple antenna zones are each coupled with a same set of PAs 108 (e.g., all PAs 108 are coupled with each antenna zone 290). Various arrangements and couplings of PAs 108 to antenna zones 290 allow the RF charging pad 151 to sequentially or selectively activate different antenna zones in order to determine the most efficient antenna zone 290 to use for transmitting wireless power to a wireless power receiver. In some embodiments, the one or more power amplifiers 108 are also in communication with the CPU subsystem 170 to allow the CPU 202 to measure output power provided by the PAs 108 to the antenna zones 110 of the RF charging pad 151.

FIG. 1C also shows that, in some embodiments, the antenna zones 290 of the RF charging pad 151 may include one or more antennas 210A-N. In some embodiments, each antenna zone of the plurality of antenna zones 290 includes one or more antennas 210 (e.g., antenna zone 290-1 includes one antenna 210-A and antenna zones 290-N includes multiple antennas 210). In some embodiments, a number of antennas included in each of the antenna zones is dynamically defined based on various parameters, such as a location of a wireless power receiver on the RF charging pad 151. In some embodiments, each antenna zone 290 may include antennas of different types, while in other embodiments each antenna zone 290 may include a single antenna of a same type, while in still other embodiments, the antennas zones may include some antenna zones that include a single antenna of a same type and some antenna zones that include antennas of different types. In some embodiments the antenna/power-transfer zones may also or alternatively include capacitive charging couplers that convey electrical signals but do not send propagating radio frequency waves.

In some embodiments, the RF charging pad 151 may also include a temperature monitoring circuit that is in communication with the CPU subsystem 170 to ensure that the RF charging pad 151 remains within an acceptable temperature range. For example, if a determination is made that the RF charging pad 151 has reached a threshold temperature, then operation of the RF charging pad 151 may be temporarily suspended until the RF charging pad 151 falls below the threshold temperature.

By including the components shown for RF power transmitter circuit 160 (FIG. 1C) on a single chip, such transmitter chips are able to manage operations at the transmitter chips more efficiently and quickly (and with lower latency), thereby helping to improve user satisfaction with the charging pads that are managed by these transmitter chips. For example, the RF power transmitter circuit 160 is cheaper to construct, has a smaller physical footprint, and is simpler to install.

FIG. 1D is a block diagram of a charging pad 294 in accordance with some embodiments. The charging pad 294 is an example of the charging pad 151 (FIG. 1B), however, one or more components included in the charging pad 151 are not included in the charging pad 294 for ease of discussion and illustration.

The charging pad 294 includes an RF power transmitter integrated circuit 160, one or more power amplifiers 108, a PA IC 161A (which may be on the same or a separate IC from the RF power transmitter IC 160), and a transmitter antenna array 290 having multiple antenna zones. Each of these components is described in detail above with reference to FIGS. 1A-1C. Additionally, the charging pad 294 includes a switch 295 (i.e., transmitter-side switch), positioned between the power amplifiers 108 and the antenna array 290, having a plurality of switches 297-A, 297-B, . . . 297-N. The switch 295 is configured to switchably connect one or more power amplifiers 108 with one or more antenna zones of the antenna array 290 in response to control signals provided by the RF power transmitter integrated circuit 160.

To accomplish the above, each switch 297 is coupled with (e.g., provides a signal pathway to) a different antenna zone of the antenna array 290. For example, switch 297-A may be coupled with a first antenna zone 290-1 (FIG. 1C) of the antenna array 290, switch 297-B may be coupled with a second antenna zone 290-2 of the antenna array 290, and so on. Each of the plurality of switches 297-A, 297-B, . . . 297-N, once closed, creates a unique pathway between a respective power amplifier 108 (or multiple power amplifiers 108) and a respective antenna zone of the antenna array 290. Each unique pathway through the switch 295 is used to selectively provide RF signals to specific antenna zones of the antenna array 290. It is noted that two or more of the plurality of switches 297-A, 297-B, . . . 297-N may be closed at the same time, thereby creating multiple unique pathways to the antenna array 290 that may be used simultaneously.

In some embodiments, the RF power transmitter integrated circuit 160 (or the PA IC 161A, or both) is (are) coupled to the switch 295 and is configured to control operation of the plurality of switches 297-A, 297-B, . . . 297-N (illustrated as a “control out” signal in FIGS. 1B and 1D). For example, the RF power transmitter integrated circuit 160 may close a first switch 297-A while keeping the other switches open. In another example, the RF power transmitter integrated circuit 160 may close a first switch 297-A and a second switch 297-B, and keep the other switches open (various other combinations and configuration are possible). Moreover, the RF power transmitter integrated circuit 160 is coupled to the one or more power amplifiers 108 and is configured to generate a suitable RF signal (e.g., the “RF Out” signal) and provide the RF signal to the one or more power amplifiers 108. The one or more power amplifiers 108, in turn, are configured to provide the RF signal to one or more antenna zones of the antenna array 290 via the switch 295, depending on which switches 297 in the switch 295 are closed by the RF power transmitter integrated circuit 160.

In some embodiments, the charging pad is configured to transmit test power transmission signals and/or regular power transmission signals using different antenna zones, e.g., depending on a location of a receiver on the charging pad. Accordingly, when a particular antenna zone is selected for transmitting test signals or regular power signals, a control signal is sent to the switch 295 from the RF power transmitter integrated circuit 160 to cause at least one switch 297 to close. In doing so, an RF signal from at least one power amplifier 108 can be provided to the particular antenna zone using a unique pathway created by the now-closed at least one switch 297.

In some embodiments, the switch 295 may be part of (e.g., internal to) the antenna array 290. Alternatively, in some embodiments, the switch 295 is separate from the antenna array 290 (e.g., the switch 295 may be a distinct component, or may be part of another component, such as the power amplifier(s) 108). It is noted that any switch design capable of accomplishing the above may be used, and the design of the switch 295 illustrated in FIG. 1D is merely one example.

FIG. 2 is a block diagram illustrating a representative transmitter device 102 (also sometimes referred to herein as a transmitter 102, a wireless power transmitter 102, and a wireless-power-transmitting device 102) in accordance with some embodiments. In some embodiments, the transmitter device 102 includes one or more processors 104 (e.g., CPUs, ASICs, FPGAs, microprocessors, and the like), one or more optional communication components 112 (e.g., radios), memory 106, one or more antennas 110, and one or more communication buses 108 for interconnecting these components (sometimes called a chipset). In some embodiments, the transmitter device 102 includes one or more sensors 114 as described above with reference to FIG. 1A. In some embodiments, the transmitter device 102 includes one or more output devices such as one or more indicator lights, a sound card, a speaker, a small display for displaying textual information and error codes, etc. In some embodiments, the transmitter device 102 includes a location detection device, such as a GPS (global positioning satellite) or other geo-location receiver, for determining the location of the transmitter device 102.

The communication components 112 enable communication between the transmitter 102 and the receiver 120 (e.g., one or more communication networks). In some embodiments, the communication components 112 include, e.g., hardware capable of data communications using any of a variety of wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread, Z-Wave, Bluetooth Smart, ISA100.11a, WirelessHART, MiWi, etc.) wired protocols (e.g., Ethernet, HomePlug, etc.), and/or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document.

The memory 106 includes high-speed random access memory, such as DRAM, SRAM, DDR SRAM, or other random access solid state memory devices; and, optionally, includes non-volatile memory, such as one or more magnetic disk storage devices, one or more optical disk storage devices, one or more flash memory devices, or one or more other non-volatile solid state storage devices. The memory 106, or alternatively the non-volatile memory within memory 106, includes a non-transitory computer-readable storage medium. In some embodiments, the memory 106, or the non-transitory computer-readable storage medium of the memory 106, stores the following programs, modules, and data structures, or a subset or superset thereof:

-   -   operating logic 216 including procedures for handling various         basic system services and for performing hardware dependent         tasks;     -   communication module 218 for coupling to and/or communicating         with remote devices (e.g., remote sensors, transmitters,         receivers, servers, etc.), in conjunction with communication         component(s) 112 and/or antenna(s) 110;     -   sensor module 220 for obtaining and processing sensor data         (e.g., in conjunction with sensor(s) 114) to, for example,         determine the presence, velocity, and/or positioning of object         in the vicinity of the transmitter 102;     -   optimal phase setting module 222 for determining an optimal         phase antenna for respective antennas in the transmitter's         antenna array 110. In some embodiments, as discussed below with         reference to FIGS. 5A-5C, the optimal phase setting module 222         determines the optimal phase setting using either a binary         search method or a least squares method, or some combination         thereof;     -   power wave generating module 224 for generating and transmitting         (e.g., in conjunction with antenna(s) 110) power waves. In some         embodiments, the power wave generating module 224 is associated         with (or includes) the optimal phase setting module 222 is used         to determine the optimal phase; and     -   database 226, including but not limited to:         -   sensor information 228 for storing and managing data             received, detected, and/or transmitted by one or more             sensors (e.g., sensors 114 and/or one or more remote             sensors);         -   test phases 230 for storing and managing predetermined test             phases of test signals transmitted by the power wave             generating module 224. In some embodiments, as discussed             below with reference to FIGS. 5A-5C, the test phases are             separated by a predetermined interval corresponding to known             characteristics of a pure sinusoidal wave;         -   optimal phases 232 for storing and managing optimal antenna             phases determined by the optimal phase setting module 222             for one or more antennas 110; and         -   communication protocol information 234 for storing and             managing protocol information for one or more protocols             (e.g., custom or standard wireless protocols, such as             ZigBee, Z-Wave, etc., and/or custom or standard wired             protocols, such as Ethernet).

Each of the above-identified elements (e.g., modules stored in memory 106 of the transmitter 102) is optionally stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing the function(s) described above. The above identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules are optionally combined or otherwise rearranged in various embodiments. In some embodiments, the memory 106, optionally, stores a subset of the modules and data structures identified above. Furthermore, the memory 106, optionally, stores additional modules and data structures not described above, such as a tracking module for tracking the movement and positioning of objects within a transmission field.

FIG. 3 is a block diagram illustrating a representative receiver device 120 (also referred to herein as a receiver 120, a wireless power receiver 120, and a wireless-power-receiving device 120) in accordance with some embodiments. In some embodiments, the receiver device 120 includes one or more processors 140 (e.g., CPUs, ASICs, FPGAs, microprocessors, and the like), one or more optional communication components 144, memory 142, one or more antennas 124, power harvesting circuitry 310, and one or more communication buses 308 for interconnecting these components (sometimes called a chipset). In some embodiments, the receiver device 120 includes one or more sensors 128 such as one or sensors described above with reference to FIG. 1A. In some embodiments, the receiver device 120 includes an energy storage device 312 for storing energy harvested via the power harvesting circuitry 310. In various embodiments, the energy storage device 312 includes one or more batteries (e.g., battery 130, FIG. 1A), one or more capacitors, one or more inductors, and the like.

As described above with reference to FIG. 1A, in some embodiments, the receiver 120 is internally or externally connected to an electronic device (e.g., electronic device 122 a, FIG. 1A) via a connection 138 (e.g., a bus). In some embodiments, the energy storage device 312 is part of the electronic device.

In some embodiments, the power harvesting circuitry 310 includes one or more rectifying circuits and/or one or more power converters. In some embodiments, the power harvesting circuitry 310 includes one or more components (e.g., a power converter 126) configured to convert energy from power waves and/or energy pockets to electrical energy (e.g., electricity). In some embodiments, the power harvesting circuitry 310 is further configured to supply power to a coupled electronic device (e.g., an electronic device 122), such as a laptop or phone. In some embodiments, supplying power to a coupled electronic device include translating electrical energy from an AC form to a DC form (e.g., usable by the electronic device 122).

The communication component(s) 144 enable communication between the receiver 120 and the transmitter 102 (e.g., via one or more communication networks). In some embodiments, the communication component(s) 144 include, e.g., hardware capable of data communications using any of a variety of custom or standard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread, Z-Wave, Bluetooth Smart, ISA100.11a, WirelessHART, MiWi, etc.) custom or standard wired protocols (e.g., Ethernet, HomePlug, etc.), and/or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document. In some embodiments, the receiver 120 may utilize a built-in communication component (e.g., a Bluetooth radio) or an electronic device with which the receiver 120 is coupled, and therefore, in these embodiments, the receiver 120 may not include its own communication component. In some other embodiments, the receiver 120 does not include a distinct communication component 144. Rather, the receiver 120 may use an in-band communication technique to communicate with other devices, as explained below with reference to FIGS. 6A-6C and FIG. 7.

The memory 142 includes high-speed random access memory, such as DRAM, SRAM, DDR SRAM, or other random access solid state memory devices; and, optionally, includes non-volatile memory, such as one or more magnetic disk storage devices, one or more optical disk storage devices, one or more flash memory devices, or one or more other non-volatile solid state storage devices. The memory 142, or alternatively the non-volatile memory within memory 142, includes a non-transitory computer-readable storage medium. In some embodiments, the memory 142, or the non-transitory computer-readable storage medium of the memory 142, stores the following programs, modules, and data structures, or a subset or superset thereof:

-   -   operating logic 314 including procedures for handling various         basic system services and for performing hardware dependent         tasks;     -   communication module 316 for coupling to and/or communicating         with remote devices (e.g., remote sensors, transmitters, other         receivers, servers, electronic devices, mapping memories, etc.)         in conjunction with the optional communication component(s) 144         and/or antenna(s) 124;     -   sensor module 318 for obtaining and processing sensor data         (e.g., in conjunction with sensor(s) 128) to, for example,         determine the presence, velocity, and/or positioning of the         receiver 120, a transmitter 102, or an object in the vicinity of         the receiver 120;     -   power receiving module 320 for receiving (e.g., in conjunction         with antenna(s) 124 and/or power harvesting circuitry 310) and         optionally converting (e.g., in conjunction with power         harvesting circuitry 310) the energy (e.g., to direct current);         transferring the energy to a coupled electronic device (e.g., an         electronic device 122); and optionally storing the energy (e.g.,         in conjunction with energy storage device 312)     -   power determining module 321 for determining (in conjunction         with operation of the power receiving module 320) an amount of         power received by the receiver based on energy extracted from         power waves (or RF test signals) and/or pockets or energy at         which the power waves converge (e.g., RF signals 116, FIG. 1A).         In some embodiments, as discussed below with reference to FIGS.         5A-5B, after determining an amount of power received by the         receiver, the receiver 120 transmits to the transmitter 102         information identifying the amount of power;     -   a switch module 330 for signaling when to open a switch of the         power harvesting circuity 310 in order to stop power surges from         damaging sensitive components. In some embodiments, as discussed         below with reference to FIGS. 5A-5B, the switch is a negative         voltage switch that is in a default-closed state;     -   A toggle module 332 for controlling the impedance mismatch in         the system, which in turn can cause a portion of the incoming         power to be reflected from the antenna of the wireless power         receiver. By modulating the amount of power reflected by the         antenna device can communicate with a wireless power transmitter         without needing a dedicate communication component (e.g., .,         IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread, Z-Wave, Bluetooth         Smart, ISA100.11a, WirelessHART, MiWi, etc.) wired protocols         (e.g., Ethernet, HomePlug, etc.). In some embodiments, as         discussed with reference to FIGS. 6A-6C below, when the toggle         602 toggles it causes the adjustable load 601 to change the         impedance of the receiver 120, which further causes incoming         power to be reflected at antenna 413; and     -   database 322, including but not limited to:         -   sensor information 324 for storing and managing data             received, detected, and/or transmitted by one or more             sensors (e.g., sensors 128 and/or one or more remote             sensors);         -   device settings 326 for storing and managing operational             settings for the receiver 120, a coupled electronic device             (e.g., an electronic device 122), and/or one or more remote             devices; and         -   communication protocol information 328 for storing and             managing protocol information for one or more protocols             (e.g., custom or standard wireless protocols, such as             ZigBee, Z-Wave, etc., and/or custom or standard wired             protocols, such as Ethernet).

In some embodiments, the power receiving module 320 communicates the amount of power to the communication module 316, which communicates the amount of power to other remote devices (e.g., transmitter 102, FIGS. 1-2). Moreover, in some embodiments, the power receiving module 320 may communicate the amount of power to database 322 (e.g., the database 322 stores the amount of power derived from one or more power waves 116). In some embodiments, the power receiving module 321 instructs the communication module 316 to transmit distinct transmissions to the remote devices (e.g., a first communication signal that indicates a first amount of power received by the receiver (e.g., by a first test signal from the transmitter 102), a second communication signal that indicates a second amount of power received by the receiver (e.g., by a second test signal from the transmitter 102), and so on if needed). Alternatively, in some embodiments, the power receiving module 320 instructs the communication module 316 to transmit data packets to the remote devices (e.g., a respective data packet can include information for multiple test signals transmitted by the transmitter 102).

Each of the above identified elements (e.g., modules stored in memory 142 of the receiver 120) is optionally stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing the function(s) described above. The above identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules are optionally combined or otherwise rearranged in various embodiments. In some embodiments, the memory 142, optionally, stores a subset of the modules and data structures identified above. Furthermore, the memory 142, optionally, stores additional modules and data structures not described above, such as an identifying module for identifying a device type of a connected device (e.g., a device type for an electronic device 122).

On-and-Off Power Detection

FIG. 4A is a schematic of a representative receiver 120 in accordance with some embodiments. The representative receiver 120 is an example of the receiver 120 (FIG. 3). The components in FIG. 4A are illustrated in a particular arrangement for ease of illustration and one skilled in the art will appreciate that other arrangements are possible. Moreover, while some example features are illustrated, various other features have not been illustrated for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

In FIG. 4A, the receiver 120 includes an antenna 413 capable of receiving wireless power transmission signals (e.g., power waves 116). Once the wireless power transmission signals are received at the antenna 413 and converted to an alternating current, the alternating current is sent to an input of the coupling mechanism 410. Some examples of coupling mechanism 410 are illustrated in FIG. 4C. In some embodiments, the coupling mechanism 410 has two outputs (a first output that supplies AC alternating current the first rectifier 401, and a second output that supplies the alternating current to the second rectifier), and each output receives a portion of the alternating current received at the input of the coupling mechanism. In some embodiments, the coupling mechanism is configured to send all but −30 dB to −40 dB of the alternating current to the first output of the coupling mechanism 410, and sending the remaining −30 to −40 dB of the alternating current to the second output of the coupling mechanism 410.

The first output of the coupling mechanism 410 is coupled to an input of an input matching network 403, which is configured to match the impedance of the first rectifier with the impedance of the antenna 413. Although one matching network 403 is shown, it is possible to have multiple input matching networks, as illustrated by numeral 403-n in FIG. 4B. The matching network is designed to match the impedance between the source (e.g., the antenna 413) and the load (e.g., the rectifier 401). The output of the matching network(s) is (are) coupled to the first rectifier 401. The first rectifier is configured to convert all but −30 dB to −40 dB of the alternating current to direct current. Some examples of rectifiers are shown in FIG. 4D. The output of the first rectifier 401 is coupled in parallel to both a capacitor 404, and the charging components Z_(L) 406. The capacitor 404, which is also coupled to the ground, is designed to reduce ripple in the direct current output by the first rectifier 401, and has a capacitance that matches a direct current of the output of the first rectifier. With larger loads (i.e., rectifier outputs), a larger capacitance may be required, and when there is a larger capacitance, the capacitor takes a longer time to charge and discharge (i.e., the voltage to reach a steady state), which slows the response time of detecting whether power is no longer being received at the antenna 413.

The second output of the coupling mechanism is coupled to the second rectifier 402. The second rectifier 402 converts the remaining −30 dB to −40 dB of the wireless power transmission signals into direct current. Since this −30 dB to −40 dB is roughly less than 1% of the amount of wireless power transmission signals received at the antenna 413, the capacitor 405 associated with the second rectifier 402 has a lower capacitance (relative to the capacitance of the capacitor 404). Consequently, the capacitor 405 in FIG. 4A can charge up and discharge rapidly in comparison to the capacitor 404 coupled to the output of the first rectifier 401. As a result, the direct current and/or voltage measuring components (“V_(AUX)”) 409-1 detect changes in direct current power levels and/or voltage levels in a shorter time span than the measuring components included in the charging components Z_(L) 406. The measuring components (“V_(AUX)”) 409-1 detect the change in wireless power transmission signals by either a change in voltage and/or direct current, and can then instruct the charging components Z_(L) 406 components to prepare for a change in power once the capacitor 404 is either discharging or fully charged.

The second rectifier 402 is also optionally coupled with two resistors in series (resistor 407 and resistor 408). Between these two resistors, a voltage measurement can also be taken, which acts as another measurement component (“V_(AUX_DIV)”) 409-2. Such an arrangement of resistors is capable of stepping down the voltage, which allows for measuring components to have a lower voltage threshold to determine whether power is increasing or no longer being received. The resistance of these resistors can be varied depending on the acceptable voltage level of the direct current measuring components. In some embodiments, these resistors are variable resistors and are adjusted by a control. Furthermore, resistor 408 is also coupled to the ground.

To help illustrate the benefits of a dual rectifier receiver, graph 400-A compares a single rectifier system against a dual rectifier system. The graph shows at time “t₁” that the RF power (i.e. the wireless power transmission signals) starts to be received at the antenna 413. “V_(OUT)” shows the output of direct current at the output of the first rectifier. “V_(AUX)” shows the measuring component 409-1, which shows the output of the second rectifier 402. And, “V_(AUX_DIV)” shows a second measurement point 409-2 that has had its voltage stepped down by the two resistors, which can be used to activate a measuring component that has a lower voltage threshold.

Moving to time “t₂” the received RF power input remains constant and does not change. At time “t₂,” the “V_(OUT)” measuring components are still seeing a rise in voltage, as opposed to a constant voltage. Only once the voltage has settled can the system utilize the converted direct current (DC) (power). While the system is waiting for the voltage to settle, it is not aware that incoming power is going to the charging components Z_(L) 406. To counteract this undesirable effect of not preparing the charging components Z_(L) 406 for the incoming power, a second rectifier 402 is used in conjunction with a capacitor 405 with a smaller capacitance (relative to capacitor 404) that allows the voltage to settle at time “t₂.” Once the voltage has settled at measuring components 409-1 and 409-2, then the system can communicate with the charging components Z_(L) 406, (e.g., warn those components that incoming power is coming despite “V_(OUT)” not yet being settled).

Only at time “t₃” does the first rectifier and capacitor 404 produce a settled voltage that can be used by the system. At time “t₃,” the RF power is no longer being received at the antenna 413. At time “t₄,” the smaller capacitance capacitor 405 is able to settle to a voltage level that indicates that there is no longer any RF power being received at the antenna 413 (e.g., 0 volts). Once this lower voltage settles, the control system can notify the charging components Z_(L) 406 that they should prepare for powering down. In contrast, at time “t₅” (i.e., long after time “t₄”), the larger capacitance capacitor 404 fully discharges and settles to the lower voltage indicating the system is no longer receiving RF power at the antenna 413. In sum, the charging components of the wireless power receiver benefit from an early warning from the smaller capacitor 405 that power is no longer being received because the charging components avoid having to wait on the capacitor's 404 long discharge time before beginning shutdown. Consequently, the early warning from the smaller capacitor 405 allows the charging components to prepare for a power down in anticipation of a loss of power, thus prolonging a life of the wireless power receiver (and potentially components in the device to be charged).

Thus, FIG. 4A at bottom describes a receiver 120 that can apportion a small amount of its received wireless power for the purpose of improving reliability of the main components of the circuit (i.e., Z_(L) 406 components) by warning these components that a change in power is occurring. This improved reliability is achieved by anticipating a shutdown, which is discussed in detail in the preceding paragraph.

FIG. 4B is a schematic that illustrates alternative embodiments to those discussed with reference to FIG. 4A. Namely, FIG. 4B shows alternative locations at which the coupling mechanism 410 can be coupled to the circuit, and still perform the same on-and-off detection as discussed in detail with respect to FIG. 4A. While some example features are illustrated, various other features, which were shown in FIG. 4A, have not been illustrated in FIG. 4D for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

The differences between FIG. 4A and FIG. 4B include the addition of first capacitor 404-a and second capacitor 404-b, and at least a second matching network identified as N^(th) input matching network 403-n. Additionally, four vertical dotted lines represent the different locations that the coupling mechanism 410 can be coupled to the circuit. As shown, the coupling mechanism can be coupled to the circuit at a point before a first capacitor 404-a. Alternatively, the coupling mechanism 410 may also be coupled after the first capacitor 404-a, but before the second capacitor 404-b. The next location at which the coupling mechanism 410 can be coupled to the circuit is the same location as the one shown in FIG. 4A. Finally, the coupling mechanism 410 can be coupled to the circuit between any of the input matching networks. This is illustrated by the coupling mechanism 410 being placed after the input matching network 403, but before the coupling mechanism 4′0 being placed before the N^(th) input matching network 403-n. In this example, the N^(th) input matching network 403-n represents the last input matching network.

FIG. 4C is schematic illustrating three separate coupling mechanism embodiments. In some embodiments, the coupling mechanism 410 is a directional coupler, shown in FIG. 4C as “Coupler A.” The directional coupler consists of two separate paths, the first path 458 and the second path 459. With reference to both FIG. 4A and FIG. 4B, the first path 458 is the path that is coupled to the antenna 413. Path 458 is also ultimately connected to the first rectifier 401. The second path 459 is placed within a certain proximity to the first path 458 so as to allow a portion of the RF signals to bleed off to the second path 459. The second path 459 is ultimately coupled to the second rectifier 402, as shown in FIG. 4A. Additionally, the second path 459 includes a resistor 456 that is coupled to a ground 457.

FIG. 4C also includes schematics for illustrating a capacitive coupler, shown in FIG. 4C as “Coupler B.” The capacitive coupler consists of two separate paths, the first path 460 and the second path 461. With reference to both FIG. 4A and FIG. 4B, the first path 460 is the path that is coupled to the antenna 413. Path 460 is also ultimately connected to the first rectifier 401. The second path 461 is coupled between the first capacitor 462 and second capacitor 463. The second path 461 is ultimately coupled to the second rectifier 402, as shown in FIG. 4A. Additionally, the second capacitor 463 is also coupled to a ground 464.

FIG. 4C also includes schematics for illustrating a resistive coupler, shown in FIG. 4C as “Coupler C.” The capacitive coupler consists of two separate paths, the first path 465 and the second path 466. With reference to both FIG. 4A and FIG. 4B, the first path 465 is the path that is coupled to the antenna 413. Path 465 is also ultimately connected to the first rectifier 401. The second path 466 is coupled between the first resistor 467 and second resistor 468. The second path 466 is ultimately coupled to the second rectifier 402, as shown in FIG. 4A. Additionally, the second resistor 486 is also coupled to a ground 469.

FIG. 4D shows two schematics for rectifiers. Rectifier “A” illustrates a diode based rectifier. With respect to the diode based rectifier, the input to the rectifier system is shown as input 448, which is coupled to an anode of a diode 450, and coupled in parallel to the cathode of a diode 451. The cathode of the diode 450 is coupled to the output of the rectifier system, as shown as output 449, while the anode of the diode 451 is coupled to the ground 452.

FIG. 4D also shows a schematic for a second rectifier, rectifier “B.” Rectifier “B” is a diode connected transistor based rectifier. With respect to diode connected transistor based rectifier, the input to the rectifier system is shown as input 448, which is coupled, in parallel, to a first diode connected transistor 453, and a second diode connected transistor 454. The first diode connected transistor 453 is coupled to the output of the rectifier system, as shown as output 449, while the second diode connected transistor 454 is coupled to the ground 455.

FIG. 4E shows a schematic of a receiver 120 that is similar to the receiver shown in FIG. 4A. The receiver shown in FIG. 4E, however, does not include a coupling mechanism. The purpose of the circuit shown in FIG. 4E is for detecting when the wireless power transmission signals are no longer being received at the antenna 413, without the use of a coupling mechanism. When the power is no longer detected the receiver can warn components that are coupled to the output of the first rectifier 401 that the charging components 406 need to prepare for shutdown.

The schematic itself shows an antenna 413 that is coupled to an input of an input matching network 403. The output of the input matching network 403 is coupled to two rectifiers 401, 402 in parallel. Some examples of more simplified rectifiers are shown in FIG. 4F. The output of the rectifier 401 is coupled in parallel to the both a capacitor 404 and charging components “Z_(L)” 406. The capacitor 404, which is also coupled to the ground 438, is designed to reduce ripple in the DC output by the first rectifier 401, and has a capacitance that matches the DC load of the output of the first rectifier 401. With larger loads, a larger capacitance is required, and with the larger capacitance, the capacitor 404 takes a longer time to charge and discharge (i.e., for the voltage to reach a steady state), which slows the response time of detecting whether power is no longer being received at the antenna 413.

The second output of the input matching network 403 is coupled to the second rectifier 402. The capacitor 405 in FIG. 4E can charge up and discharge more rapidly in comparison to the capacitor 404 coupled to the output of the first rectifier 401. With respect to the ripple from the output of the rectifier 402, the components coupled to the output of the rectifier 402 require a less drastic ripple reduction as compared to the components coupled to the output of the rectifier 401. As a result, a smaller capacitance capacitor 405 can be used that allows for faster discharge times and, consequently, the DC and/or voltage measuring components (“V_(AUX)”) 409-1 detect changes in DC power levels and/or voltage levels in a shorter time span than the measuring components included in the charging components Z_(L) 406. The measuring components (“V_(AUX)”) 409-1 detect the change in wireless power transmission signals by a change in voltage and/or DC current, and can then instruct the charging components Z_(L) 406 to prepare for a change in power once the capacitor 405 either starts discharging or is fully discharged.

In some embodiments, the second rectifier 402 is also optionally coupled to two resistors in series (resistor 407 and resistor 408, which are coupled to the ground 437). Between these two resistors a voltage measurement can also be taken, which acts as another measurement component (“V_(AUX_DIV)”) 409-2. Such an arrangement of resistors is capable of stepping down the voltage, which allows for measuring components to have a lower voltage threshold to determine whether power is no longer being received. The resistance of these resistors can be varied depending on the acceptable voltage level of the DC measuring components. In some embodiments, these resistors are variable resistors and are adjusted by a control.

To help illustrate the benefits of a dual rectifier receiver, graph 400-B compares a single rectifier system to a dual rectifier system. The graph shows at time “t₁” that RF power (i.e. wireless power transmission signals) are received at the antenna 413. “V_(OUT)” shows the output of DC at the output of the first rectifier. “V_(AUX)” shows the measuring component 409-1, which shows the output of the second rectifier 402. And, “V_(AUX_DIV)” shows a second measurement point 409-2 that has had its voltage stepped down by the two resistors, which can be used to activate a measuring component that has a lower voltage threshold.

At time “t₂”, the first rectifier 401 and capacitor 404 produce a settled voltage that can be used by the charging components Z_(L) 406. Also at time “t₂”, the RF power is no longer being received at the antenna 413. At time “t₃”, the smaller capacitance capacitor 405 is able to settle to a voltage level that indicates that there is no longer any RF power being received at the antenna 413. Once this lower voltage settles (e.g., at 0 volts), the system can notify the charging components Z_(L) 406 that they should prepare for powering down. In contrast, it is not until time “t₄” that the larger capacitor 404 fully discharges and settles to the lower voltage indicating the system is no longer receiving RF power at the antenna 413. Warning (i.e., signaling) the charging components that RF power is no longer being received is beneficial so that those components can prepare for a shutdown in anticipation of a loss of power. Without the second rectifier 402, the charging components would have to rely solely on the first rectifier 401 and the larger capacitor 404 to prepare for shutdown, which as explained above is not ideal because the larger capacitor 404 takes a significant amount of time to fully discharge (i.e., an adequate warning cannot be given to the charging components when the larger capacitance capacitor 404 is solely relied upon).

In sum, FIG. 4E ultimately describes a receiver 120 that can apportion a small amount of its received wireless power for the purpose of improving reliability of the main components of the circuit (i.e., Z_(L) 406 components) by warning these components that the RF power is no longer being received at the antenna 413.

Transitioning to FIG. 4F, FIG. 4F illustrates two simplified rectifiers that are optionally used in rectifiers 401 and 402 in FIG. 4E. These simplified rectifiers are similar to those shown in FIG. 4D, however, since the input of the first rectifier is couple to the input of the second rectifier, the second rectifier can be made simpler. Although FIG. 4F shows examples of some rectifiers, any possible diode connected configuration which has reverse bias cut-off characteristics can be used instead. With respect to the second rectifier 402, in some embodiments the second rectifier 402 is on the same or separate integrated circuit as the first rectifier (i.e., main rectifier) 401. The second rectifier (i.e., auxiliary rectifier) 402, in some embodiments, is a discrete system on a printed circuit board, package, and/or module.

Power Surge Protection

FIG. 5A is a schematic of a representative receiver 120 in accordance with some embodiments. The representative receiver 120 is an example of the receiver 120 (FIG. 3). The components in FIG. 5A are illustrated in a particular arrangement for ease of illustration and one skilled in the art will appreciate that other arrangements are possible. Moreover, while some example features are illustrated, various other features have not been illustrated for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

In FIG. 5A, the receiver 120 includes an antenna 413 capable of receiving wireless power transmission signals (also referred to as RF power). Once the wireless power transmission signals are received at the antenna 413 and converted to an alternating current, the alternating current is sent to an input of the coupling mechanism 410. Some examples of coupling mechanism 410 are illustrated in FIG. 4C. In some embodiments, the coupling mechanism 410 has two outputs (a first output that supplies the alternating current to the first rectifier, and a second output that supplies the alternating current to the second rectifier), and each output receives a portion of the alternating current received at the input of the coupling mechanism 410. In some embodiments, the coupling mechanism 410 is optionally configured to send all but −30 dB to −40 dB of the alternating current to the first output of the coupling mechanism 410, and sending the remaining −30 to −40 dB of the alternating current to the second output of the coupling mechanism 410.

A first output of the coupling mechanism 410 is coupled to an input of an input matching network 403, which is configured to match the impedance of the rectifier 401 with the impedance of the antenna 413. Additionally, it is possible to have multiple input matching networks, as illustrated by numeral 403-n. The matching network is designed to match the impedance between the source (e.g., the antenna) and the load (e.g., the rectifier). The output of the matching network(s) is coupled to the first (i.e., primary) rectifier 401. The output of the rectifier 401 is coupled to a capacitor 503. The capacitor 503, which is also coupled to the ground 504, is designed to reduce ripple in the system, and has a capacitance that matches the DC load of the output of the first rectifier 401. With larger loads, a larger capacitance is required to reduce the ripple, so as to not damage the charging components represented by numeral 505.

A second output of the coupling mechanism 410 is coupled to the second rectifier 510 (also referred to as an auxiliary or secondary rectifier). The second rectifier 510 (also referred to as the negative voltage generator) converts its received wireless power transmission signals into negative voltage. The output of the second rectifier 510 is coupled to a “normally on” active switch 501 that has a gate voltage of 0 volts when turned on (i.e., a switch that is in a normally closed state that couples the circuit to the ground 502, which causes an impedance mismatch between the rectifier 401 and the antenna 413, which in turn causes the wireless power transmission signals to be reflected by the antenna). The switch 501, when coupled to the ground 502, pulls the output of the rectifier 510 to 0 volts. In other words, when the voltage falls below 0 volts, the switch 501 will gradually begin to open, which causes some of the negative voltage to not be directed to the ground 502, but instead back to the first output of the coupling mechanism 410. Optionally, as depicted by FIG. 5A, the output of the rectifier 510 can be coupled either to the first output of the coupling mechanism 410, before or after the input matching network, between two or more matching networks, or before or after the first rectifier 401. When the switch 501 allows for some of the current to be directed to the ground 502, an impedance mismatch is created between the antenna and the first rectifier 401. Once the gate 501 is fully opened and the current with the negative voltage is no longer being directed to the ground, then the first rectifier 401 can match the impedance of the antenna 413, and the wireless power transmission signals will not be reflected by the antenna 413.

To illustrate the discussion above, graph 500 shows the gradual opening of the switch 501 stopping the rectifier 401 from receiving a power surge. As shown in the first top row 500-A of the graph 500, the RF input power (i.e., the wireless power transmission signals that are converted to an alternating current) is received at the antenna 413. The wireless power transmission signals are constant beginning at time “t₁.” The second row 500-B, “Vi_coupled,” illustrates the amount of wireless power transmission signals harvested by the antenna 413 (and converted to the alternating current), and subsequently apportioned by the coupling mechanism 410. Numeral 506 illustrates the point at which “Vi_coupled” is measured. “Vi_coupled” is constant at time “t₁,” which corresponds to the amount of wireless power transmission signals being received at the antenna 413. However, only a portion of the power is received at “Vi_coupled” because of the coupling mechanism 410. Even at time “t₂”, the amount of the alternating current measured at “Vi-Coupled” remains constant, due to the coupling mechanism's 410 apportionment. In some embodiments, the coupling mechanism 410 can dynamically adjust the amount of power that is sent to the negative voltage rectifier 510.

The third row 500-C of graph 500 illustrates the negative voltage measured at point 507 in the circuit illustrated in FIG. 5A. At time “t₁,” which is the same time that the antenna 413 started to receive the alternating current, the rectifier 510 (e.g., a negative voltage generator) begins converting the alternating current to a negative voltage. The negative voltage slowly starts to increase in magnitude until time “t₂,” which at that point the negative voltage has reached a negative voltage threshold.

The fourth row 500-D illustrates the Q_(R) switch's (i.e., the switch 501) status. In other words, the fourth row 500-D shows that, depending on the negative voltage produced by the negative voltage generator 510, the switch 501 can exist in an on state (“ON”), a partially-on state that is below the negative voltage threshold (“Sub_Vth”), and a completely off state (“OFF”). At any time where the receiver does not receive any wireless power transmission signals, the switch 501 will be in the “ON” state, and will direct incoming current to the ground 502 causing an impedance mismatch at the rectifier 401. This impedance mismatch causes the wireless power transmission signals to be reflected at the antenna 413. At time “t₁”, the alternating current starts to be received at the negative voltage generator 510, and then the negative voltage generator 510 starts producing negative voltage, as discussed above with reference to the row 500-C. Once the negative voltage starts being produced, the switch 501 begins to open, which gradually uncouples the circuit at that point from the ground 502. At time “t₂”, the negative voltage threshold is met, and the switch 501 is completely open and no longer couples the ground 502 to the circuit. This consequently reduces the impedance mismatch between the first rectifier 401 and the antenna 413, and results in less reflection of the wireless power transmission signals.

The fifth row 500-E of graph 500 illustrates the amount of power that is either reflected or received at the antenna 413 due to the impedance mismatch caused by the switch either being coupled, partially coupled, or uncoupled with the ground 502. Specifically, at time “t₁”, the amount of the wireless power transmission signals reflected is at its highest, meaning that all but the wireless transmission signals apportioned by the coupling mechanism 410 to be sent to the negative voltage generator 510 are reflected at the antenna 413, which is caused by the impedance mismatch between the antenna 413 and the first rectifier 401. As the switch 501 begins to open between times “t₁” and “t₂”, the impedance mismatch begins to decrease, and as the mismatch begins to decrease, the wireless power transmission signals are reflected at a lesser rate. When the wireless power transmission signals are no longer reflected, they are directed to the first rectifier 401. After time “t₂”, the voltage threshold of the switch 501 is met the amount of reflected wireless transmission signals is decreased to its lowest state.

The sixth row 500-F of graph 500 illustrates the amount of wireless power transmission signals converted to direct current (“V_(RECT)”) by the first rectifier 401. The measuring point of “V_(RECT)” occurs at point 509. At time “t₁”, the rectifier 401 rectifies a portion of the alternating current received at the antenna 413 corresponding to the impedance mismatch caused the state of the switch 501. Additionally, at time “t₁”, the switch 501 is still primarily coupled to the ground 502, and consequently, the impedance mismatch is still high, meaning that the wireless power transmission signals are reflected by the antenna 413. Since the majority of the wireless power signals are being reflected, the rectifier 401 is not capable of producing a large amount of rectified power. At time “t₂”, when the switch 501 is no longer coupled to the ground 502, the impedance mismatch between the rectifier 401 and the antenna 413 is eliminated, thereby allowing the rectifier 401 to receive the alternating current from the antenna 413.

The seventh row 500-G of graph 500 illustrates measuring point 508 in FIG. 5A. Specifically, row 500-G illustrates what current would be received at the input of the rectifier 401 without the negative voltage generator 510 and switch 501 (i.e. the surge protector components). In the graph 500, the current that is received at the input of the rectifier 401 is referred to as “I_(RIN) without surge protection.” As shown in row 500-G, after time “t₁” a large current spike is shown, which can cause damage to the first rectifier 401, and other related charging components. After the current spike, the current plateaus and no longer has any large variations in magnitude.

The eighth row 500-H of graph 500 illustrates detected current at measuring point 508 in FIG. 5A. Specifically, row 500-G shows the measurement of the current that is received at the input of the rectifier 401, when the negative voltage generator 510 and switch 501 (i.e. the surge protector components coupled to the circuit) stop surges in power. This is shown to contrast row 500-G, which shows the current that would be flowing to the rectifier 401 if there was no surge protection. In the graph, the current with surge protection is referred to as “I_(RIN) with surge protection.” As shown in 500-H, after time “t₁” a gradual increase in current is shown, instead of a large spike as shown in 500-G, that reduces damage to the first rectifier 401 and other related components. After the switch 501 is fully opened the current plateaus and no longer has any large variations in its magnitude.

FIG. 5B is a schematic that illustrates alternative embodiments to those presented in FIG. 5A. Namely, FIG. 5B shows alternative locations at which the coupling mechanism 410 can be coupled to the circuit, and still perform the same surge protection as discussed in detail with respect to FIG. 5A. While some example features are illustrated, various other features, which were shown in FIG. 5A, have not been illustrated in FIG. 5B for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

The differences between FIG. 5A and FIG. 5B include the addition of first capacitor 404-a and second capacitor 404-b, and at least a second matching network identified as N^(th) input matching network 403-n. Additionally, six vertical dotted lines represent the different locations that the coupling mechanism 410 can be coupled to the circuit. As shown, the coupling mechanism 410 can be coupled to the circuit at a point before a first capacitor 404-a. Alternatively, the coupling mechanism 410 may be coupled after the first capacitor 404-a, but before the second capacitor 404-b. The next location at which the coupling mechanism 410 can be coupled to the circuit is at the same location as the one shown in FIG. 5A. The coupling mechanism 410 can be coupled to the circuit between any of the input matching networks. This is illustrated by the coupling mechanism 410 being placed after the input matching network 403, but before the coupling mechanism 410 being placed before the N^(th) input matching network 403-n. In this example, the N^(th) input matching network 403-n represents the last input matching network. The coupling mechanism 410 can also be placed after the last input matching network in the series of input matching networks, but before the first rectifier 401. Finally, the coupling mechanism 410 may also be placed after the rectifier 401, but before the capacitor 404 and Z_(L) 406, which represent the charging components that the receiver is coupled to.

In-Band Communication

Transitioning to FIG. 6A, FIG. 6A illustrates a way for in-band communication between a wireless power receiver 120 and a wireless power transmitter 102 without a dedicated communication radio for controlling the power of the wireless power transmission signals. The components in FIG. 6A are illustrated in a particular arrangement for ease of illustration and one skilled in the art will appreciate that other arrangements are possible. Moreover, while some example features are illustrated, various other features have not been illustrated for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

FIG. 6A's schematic illustrates one embodiment of a receiver 120. Receiver 120 includes an antenna 413 capable of receiving wireless power transmission signals. Once the wireless power transmission signals are received at the antenna 413 and converted to an alternating current, the wireless power transmission signals are sent to an input of the coupling mechanism 410. Some examples of coupling mechanism 410 are illustrated in FIG. 4C. The coupling mechanism 410 has two outputs (a first output that supplies alternating current to the first rectifier 401, and a second output that supplies alternating current to the second rectifier 402), and each output receives a portion of the alternating current received at the input of the coupling mechanism 410. In some embodiments, the coupling mechanism 410 is optionally configured to send all but −30 dB to −40 dB of the alternating current to the first output of the coupling mechanism 410, and sending the remaining −30 to −40 dB of the alternating current to the second output of the coupling mechanism 410.

A first output of the coupling mechanism 410 is coupled to an input of an input matching network 403, which is configured to match the impedance of the rectifier 402 with the impedance of the antenna 413. Additionally, it is possible to have multiple input matching networks, as illustrated by 403-n in FIG. 6B. The matching network is designed to match the impedance between the source (e.g., the antenna 4123) and the load (e.g., the rectifier 401). The output of the matching network(s) is (are) coupled to the first (i.e., primary) rectifier 401. The output of the first rectifier 401 is coupled in parallel to the both a capacitor 404 and Z_(L) 406, which represent the charging components that the receiver is coupled to. The capacitor 404, which is also coupled to the ground, is designed to reduce ripple of the direct current output by the first rectifier 401 in the system, and has a capacitance that matches the direct-current load of the output of the first rectifier 401. With larger loads (i.e., the rectifier output), a larger capacitance is required, and when there is a larger capacitance, the capacitor takes a longer time to charge and discharge (i.e., for voltage to reach a steady state), which slows the response time of detecting whether power is no longer or is being received at the antenna 413.

A second output of the coupling mechanism 410 is coupled to another input matching network 414. A second rectifier 402 (also referred to as an auxiliary or secondary rectifier) is coupled to the output of the other (also referred to as the auxiliary input matching network) input matching network 414. The second rectifier 402 converts the apportioned alternating current received from the coupling mechanism 410 to direct current with a voltage component. The second rectifier 402 is coupled to an adjustable load 601 that can cause a slight impedance mismatch of the other matching network 414. This ultimately causes a portion of wireless transmission signals to be reflected by the antenna 413 back to the transmitter 102. The adjustable load 601 is coupled to a toggle 602, and when the toggle 602 is toggled, it causes the adjustable load 601 to be toggled between two different impedances. The purpose of such an adjustable load 601 is to modulate the amount of power reflected by the receiver 120 in order to communicate with the transmitter 102.

As previously discussed, input matching quality of an RF system determines the amount of power reflected from the antenna 413. In a perfectly matched system there is no reflected power. However, when there is an impedance mismatch, some of the wireless power transmission signals are reflected from the antenna 413. Reflected wireless power transmission signals can be detected with a RF signal receiving circuitry at the transmitter 102. These reflected signals can be used by the transmitter 102 to determine how much power to send to the receiver 120, or when to stop transmitting power to the receiver 120 (e.g., the battery is sufficiently charged and no longer needs to receive power). To communicate with the transmitter 102, the receiver 120 needs to modulate the impedance (i.e., so that the reflected signals convey information). This process will be further discussed in relation to the graph 600 in FIG. 6A.

FIG. 6A's graph 600 demonstrates how the receiver 120 is able to communicate with the transmitter 102 by modulating its impedance at the auxiliary matching network. FIG. 6A includes a first row 600-A illustrating the amount of RF power (also referred to as wireless power transmission signals) that the antenna 413 is receiving. Between time “t₁” and “t₃”, there is no impedance mismatch, and the full amount of wireless power transmission signals is received by the antenna 413 (e.g., no signals are reflected at the antenna 413). However, at time “t₃” to “t₄”, an impedance mismatch is introduced into the system, which results in the amount of RF power received by the antenna 413 to decrease (i.e., some signals are reflected at the antenna 413). As shown at times “t₄” and “t₅”, the toggle 602 (also referred to as “V_(CTR)”), is switched on and off causing the reflection of wireless power transmission signals to be modulated from no reflection to partial reflection. Various aspects of the “V_(CTR)” such as frequency, duty cycle, pulse width and patterns can be used as a form of signal generation (e.g., modulation). This modulation can be used to communicate with the transmitter 102 by interpreting certain modulations as instructions regarding, e.g., how much power the transmitter 102 should be sending to the receiver 120. In some embodiments, as illustrated in row 600-A, the modulation received between times “t₄” to “t₅” causes the transmitter 102 to stop transmitting wireless transmission signals. As a result, after time “t5” the antenna 413 no longer receives wireless power transmission signals from the transmitter 102. In some embodiments, the transmitter 102 includes a demodulator that allows the transmitter 102 to demodulate and process the modulated signals generated by the receiver 120. The modulated signals can provide other information in addition to a power requirement for the receiver 120. For example, the modulated signals indicate a location of the receiver 120 relative to the transmitter 102. In another example, the modulated signals may be associated with an authorization key for the receiver 120 (i.e., once the transmitter 102 receives and processes the authorization key, the transmitter 102 initiates wireless charging of the receiver 120). Various other forms of information may conveyed using the modulated signals discussed herein.

In FIG. 6A's graph 600, the second row 600-B shows the voltage that rectifier 401 is outputting. This measurement point is taken after the capacitor 404, and is represented by numeral 603 in the circuit schematic in FIG. 6A. Between times “t₁” and “t₂”, the capacitor 404 is charging up, and only once fully charged does the voltage plateau and remain at a constant magnitude. Between times “t₃” and “t₄”, the impedance is adjusted. This impedance adjustment, however, is made only in relation to the other input matching network 414, which means that the alternating current sent to the first rectifier 401 by the coupling mechanism 410 remains the same. Therefore, between times “t₃” and “t₅”, the rectifier 401 is able to output the same amount of rectified power despite toggle 602 toggling the impedance of the other input matching network 414.

In FIG. 6A's graph 600, the third row 600-C shows the toggle 602 (also referred to as the (“V_(CTR)”)) toggling the load impedance of the input matching network 414. From times “t₁” to “t₃”, the toggle 602 is in a first state causing a certain load impedance. In some embodiments, there is no load impedance between the antenna 413 and the other input matching network 414, and none of the wireless power transmission signals are reflected by the antenna 413. Between times “t₃” and “t₄”, the toggle 602 is in a second state that causes a certain load impedence. The load impedance generated by the toggle 602 being toggled results in a mismatch with the antenna's 413 impedance, which causes a portion of the wireless power transmission signals to be reflected back to the transmitter 102. This reflected portion of the wireless power transmission signals is normally not reflected by the antenna 413 (e.g., when the toggle is in the first state).

In FIG. 6A's graph 600, the fourth row 600-D shows the output voltage by the second rectifier 402 in response to the toggling of the load impedance of the input matching network 414. The point at which the output voltage of the second rectifier 402 is demonstrated by numeral 604 in FIG. 6A's circuit schematic. Between times “t₁” and “t₃”, the toggle 602 is in the first state (i.e., no impedance mismatch with antenna 413) while between times “t₃” to “t₄”, the toggle 602 is in the second state. Again, when the toggle 602 is in the second state, the impedance mismatch is greater at the other input matching network 414, and when the impedance mismatch is greater, a greater percentage of the wireless power transmission signals are reflected by the antenna 413.

In FIG. 6A's graph 600, the fifth row 600-E shows the amount of wireless power transmission signals that are reflected by antenna 413 when the toggle 602 is in the second state. In some embodiments, when the toggle 602 is in the first state (discussed above), the toggle 602 causes the adjustable load 601 to be adjusted and cause a perfect impedance match between the other input matching network 414 and the antenna 413, which is illustrated by times “t₁” to “t₃” and portions of “t₄” to “t₅.” At these times, an amount of wireless power transmission signals reflected by the antenna 413 is minimal (if any). At times “t₃” to “t₄” and portions of time “t₄” to “t₅,” however, the toggle 602 is in the second state, which causes the adjustable load 601 to be adjusted, which ultimately causes an impedance mismatch between the antenna 413 and the other input matching network 414. When there is an impedance mismatch, at least some of the wireless transmission signals are reflected by the antenna 413, which is shown at times “t₃” to “t₄” and portions of time “t₄” to “t₅.” Although two states of modulation are discussed, it is possible to modulate the toggles frequency, duty cycle, pulse, width, and patterns.

FIG. 6B is a schematic that illustrates alternative embodiments to those presented in FIG. 6A. Namely, FIG. 6B shows alternative locations at which the coupling mechanism 410 can be coupled to the circuit and still perform the same in-band communication techniques discussed in detail with respect to FIG. 6A. While some example features are illustrated, various other features, which were shown in FIG. 6A, have not been illustrated in FIG. 6B for the sake of brevity and so as not to obscure pertinent aspects of the example implementations disclosed herein.

The differences between FIG. 6A and FIG. 6B include the addition of first capacitor 404-a and second capacitor 404-b, and at least a second matching network that is coupled to the first rectifier 401, which is identified as N^(th) input matching network 403-n. Additionally, five vertical dotted lines represent different locations that the coupling mechanism 410 can be coupled to the circuit. As shown, the coupling mechanism 410 can be coupled to the circuit at a point before a first capacitor 404-a. Alternatively, the coupling mechanism 410 may be coupled after the first capacitor 404-a, but before the second capacitor 404-b. The next location at which the coupling mechanism 410 can be coupled to the circuit of receiver 120 is at the same location as the one shown in FIG. 6A. The coupling mechanism 410 can be coupled to the circuit between any of the input matching networks. This is illustrated by the coupling mechanism 410 being placed after the input matching network 403, but before the coupling mechanism 410 being placed before the N^(th) input matching network 403-n. In this example, the N^(th) input matching network 403-n represents the last input matching network. Finally, the coupling mechanism 410 can be placed after the last input matching network in the series of input matching networks, but before the first rectifier 401.

Finally, FIG. 6C illustrates three separate embodiments for adjusting the load of the adjustable load 601, two of which are digital adjustable loads, and one of which that is an analog adjustable load. In some embodiments, a single bit digital control can be used. In some other embodiments, multiple bits can be utilized to increase the resolution/range of the signals that are being generated by the circuit (as shown in in the circuit schematic of FIG. 6A). Although three embodiments are shown, any equivalent means for adjusting the load can also be used instead. In some embodiments, the adjustable load is a tapped switch with a series of resistors, which is shown in the adjustable load 601-A. Looking at adjustable load 601-A, it includes an input point 616, which corresponds to the input of the adjustable load where the adjustable load 601-A receives rectified power from the second rectifier 402, as shown in FIG. 6A's circuit schematic. The input point 616 is coupled in parallel to the input of a capacitor 617 and an input of a resistor 619. The output of the capacitor 617 is coupled to the ground 618. The output of the resistor 619 is coupled in parallel to the input of a resistor 620 and the input to a switch 622. The output of the resistor 620 is coupled to the ground 621. The switch 622 switches when the toggle 602 toggles between its two states (e.g., connected to the ground, or unconnected from the ground), as discussed in detail in FIG. 6A. When the toggle 602 causes the switch 622 to connect to the ground 641, the impedance is subsequently changed, which can cause an impedance mismatch between the other input matching network 414 and the antenna 413, as shown in FIG. 6A.

In some embodiments, the adjustable load is a series switch with parallel resistors, which is shown in the adjustable load 601-B. This adjustable load in this example is a digital adjustable load. In some embodiments, a single bit digital control can be used. In some other embodiments, multiple bits can be utilized to increase the resolution/range of the signals that are being generated by the circuit (as shown in in the circuit schematic of FIG. 6A). Looking at adjustable load 601-B, it includes an input point 616, which corresponds to the input of the adjustable load where the adjustable load 601-B receives rectified power from the second rectifier 402, as shown in FIG. 6A's circuit schematic. The input point 616 is coupled in parallel with the input of a capacitor 623, the input of resistor 625, and the input of a resistor 627. The output of the capacitor 623 is coupled to the ground 624. The output of the resistor 625 is coupled to the ground 626. The output of the resistor 627 is coupled to a switch 628. The switch 628 switches when the toggle 602 toggles between its two states (e.g., connected to the ground 629, or unconnected from the ground 629), as discussed in detail in FIG. 6A. When the toggle 602 causes the switch 628 to connect to the ground 629, the impedance is subsequently changed. This causes an impedance mismatch between the other input matching network 414 and the antenna 413, as shown in FIG. 6A.

In some embodiments, the adjustable load is an analog control and load that allows for increased resolution/range of control of the load impedance, which is shown in the adjustable load 601-C schematic. Looking at adjustable load 601-C, it includes an input point 616, which corresponds to the input of the adjustable load where the adjustable load 601-C receives rectified power from the second rectifier 402, as shown in FIG. 6A's circuit schematic. The input point 616 is coupled in parallel to the input of a capacitor 630, the input of resistor of a variable resistor 632, and the input of a resistor 627. The output of the capacitor 623 is coupled to the ground 624. The output of the resistor 625 is coupled to the ground 626. The output of the resistor 627 is coupled to a switch 628. The switch 628 switches when the toggle 602 toggles between its two states (e.g., connected to the ground, or unconnected from the ground), as discussed in detail in FIG. 6A, and the ground 629. When the toggle 602 causes the switch 628 to connect to the ground 629, the impedance is subsequently changed, which can cause an impedance mismatch between the other input matching network 414 and the antenna 413, as shown in FIG. 6A.

FIG. 7 shows a method flowchart 700 that describes a process of communication between a wireless power receiver (e.g., receiver 120 in FIG. 6A) and a wireless power transmitter (e.g., transmitter 102). In FIG. 6A, the receiver 120 includes a rectifier 402 (sometimes called a secondary rectifier or an auxiliary rectifier) that is not used to directly power the main system (e.g., the components that allow the wireless power receiver to use the received energy). One or more operations of the method 700 may be performed by the wireless power receiver or by one or more components thereof (e.g., those described above with reference to FIG. 3). FIG. 7 corresponds to instructions stored in a computer memory or computer-readable storage medium (e.g., memory 142 of the receiver 120, FIG. 3).

In some embodiments, the method flowchart 700 includes receiving (702), by an antenna (e.g., antenna 413, FIG. 6A) of the wireless power receiver, radio frequency (RF) signals from the wireless power transmitter. During the receiving (702) (at least initially), the wireless power receiver substantially matches an impedance of the wireless power transmitter.

Moreover, while receiving the RF signals, the method 700 further includes determining (704) whether a communication criterion is satisfied. In some embodiments, the communication criterion is satisfied when an electronic device serviced by the wireless power receiver is fully charged. Alternatively or in addition, in some embodiments, the communication criterion is satisfied when there is no obstruction (or less than a predetermined level of obstruction) between the wireless power receiver and the wireless power transmitter, and the communication criteria is not satisfied when there is an obstruction (or more than a predetermined level of obstruction). In some instances, obstructions may include one or more of humans, pets, or other items that interfere with the wireless transmission of power, or cause harm to living things.

In some embodiments, in accordance with a determination that the communication criterion is not satisfied (704-No), the method 700 remains unchanged. In other words, the wireless power receiver continues to receive the RF signals from the wireless power transmitter.

In some embodiments, in accordance with a determination that the communication criterion is satisfied (704-Yes), the method 700 includes introducing (706) an impedance mismatch between the wireless power receiver and the wireless power transmitter that causes a portion of the RF signals to be reflected by the receiver's antenna as a modulated signal. In some instances, the wireless power transmitter receives and interprets the modulated signal without using a separate communication radio (e.g., a Bluetooth radio is not needed to interpret the modulated signal). Rather, the wireless power transmitter is able to receive and interpret the modulated signal using the same antenna(s) that transmitted the RF signals in the first place. In some embodiments, the portion can be capped at a certain threshold to stop the receiver from reflecting too much power back to the transmitter.

In some embodiments, introducing (706) the impedance mismatch includes creating (708) one or more impedance mismatches between the wireless power receiver and the wireless power transmitter interspersed with one or more impedance matches between the wireless power receiver and the wireless power transmitter forming the modulated signal. Interspersing impedance matches and mismatches to form a modulated signal is discussed in further detail above with reference to FIGS. 6A-6C.

In some embodiments, the wireless power receiver includes an auxiliary rectifier, coupled to the antenna, that receives some of the RF signals. In such embodiments, introducing (706) the impedance mismatch between the wireless power receiver and the wireless power transmitter includes adjusting a load of the auxiliary rectifier. The auxiliary rectifier may be a rectifier that is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode, and (iii) a second diode, and the input of the secondary rectifier is coupled to: a cathode of a first diode, wherein an anode of the first diode is coupled to a ground; and an anode of a second diode, wherein a cathode of the second diode is coupled to an output of the secondary rectifier. Alternatively, the auxiliary rectifier may be a rectifier that is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode-connected transistor, and (iii) a second diode-connected transistor, and the input of the secondary rectifier is coupled to: (a) a first diode-connected transistor, wherein the first diode-connected transistor is connected to a ground, and (b) a second diode-connected transistor, wherein the second diode-connected transistor is connected to an output of the secondary rectifier.

In some embodiments, the wireless power receiver includes an auxiliary matching network coupled to and positioned between the antenna and the auxiliary rectifier. Furthermore, adjusting the load of the auxiliary rectifier can cause a mismatch of the auxiliary matching network, which results the portion of the RF signals being reflected by the antenna. Moreover, the wireless power receiver may also include a toggle coupled to a load-adjusting mechanism (e.g., a portion of the circuit may be connected by a switch when then toggle is in one state, and disconnected when the toggle is in another state, which can change the impedance of the circuit, see also FIG. 6C illustrating three different types of mechanisms for adjusting the load), and the load-adjusting mechanism is coupled to the auxiliary rectifier (e.g., the adjustable loads components shown in FIG. 6C). Furthermore, toggling the switch (e.g., switch 602 as shown in FIG. 6C) causes a change within the load-adjusting mechanism that produces a change in the load of the receiver, which results in the impedance mismatch between the wireless power receiver and the wireless power transmitter. In some embodiments, adjusting the load of the auxiliary rectifier is done by coupling an output of the auxiliary rectifier to a load adjusting mechanism, in parallel, to (i) a capacitor, which is coupled to a ground, and (ii) a first resistor, where the first resistor is coupled, in parallel, to a second resistor in series, which is coupled to a ground, and a tapped switch coupled to the output of the first resistor in series, and a ground. The tapped switch is coupled to a toggle for opening and closing the tapped switch. In some embodiments, the load adjusting mechanism comprises (i) a capacitor, which is coupled to a ground, (ii) a first resistor, and (iii) a second resistor, where the second resistor is coupled to a series switch, which is coupled to a ground. The series switch is coupled to a toggle for opening and closing the series switch. In some embodiments, adjusting the load of the auxiliary rectifier is done by coupling the output of the auxiliary rectifier, in parallel, to (i) a capacitor, which is coupled to a ground, (ii) a variable resistor, which is coupled to a ground. The variable resistor is coupled to a toggle for adjusting the resistance of the variable resistor.

In some embodiments, in response to the wireless power receiver sending the modulated signal, the wireless power transmitter may interpret the modulated signal as an instruction to cease sending the RF signals to the wireless power receiver. In some other embodiments, in response to the wireless power receiver sending the modulated signal, the wireless power transmitter may interpret the modulated signal as an instruction to adjust transmission characteristics of the RF signals to the wireless power receiver (e.g., increase or decrease a power of the RF signals, among other adjustments). In some embodiments, the adjustment is dynamic and depends on the capabilities of the transmitter to handle reflected signals.

In some embodiments, after introducing the impedance mismatch and while continuing to receive the RF signals from the wireless power transmitter, the method further includes matching (710) the impedance between the wireless power receiver and the wireless power transmitter, which stops reflection of the portion of the RF signals by the antenna. In some embodiments, the wireless power transmitter ceases to transmit the RF signals to the wireless power receiver in response to receiving the modulated signal from the wireless power receiver. In some embodiments, in response to the wireless power receiver sending the modulated signal, the transmitter determines that a threshold amount of the reflected signal indicates that the receiver no longer requires RF signals, and as a result the wireless power transmitter stops transmitting RF signals to the wireless power receiver. In some embodiments, when a certain percentage is reflected back from the wireless power receiver, but does not exceed a threshold to stop sending power, the wireless power transmitter can adjust the amount of RF signals it is sending to the wireless power receiver.

In light of the principles discussed above, the following embodiments relate to converting energy from the received RF signals into an alternating current.

In some embodiments, a wireless power receiver is provided that comprises: a wireless-power-receiving antenna configured to receive radio frequency (RF) power signals, and convert energy from the received RF signals into an alternating current. In some embodiments, the coupler can be coupled to an output of a first capacitor, and the capacitors input is coupled to the antenna. In some embodiments, the coupler can be coupled to the output of a series of capacitors that are coupled to the antenna. In some embodiments, the coupler can be coupled to the output of the primary rectifier. In some embodiments, the coupler can be coupled after a series of capacitors. In such an embodiment, the capacitors are used to isolate the coupling point. In some embodiments, the coupler can be coupled to the output of a matching network, or the output of a series of matching networks. In some embodiments, a wireless power receiver comprises a primary rectifier configured to: (i) receive a first portion of the alternating current, and (ii) rectify the first portion of the alternating current into primary direct current having a first voltage and a first power level, the primary direct current used to provide power or charge to an electronic device. In some embodiments, the primary rectifier is coupled to a capacitor to reduce ripple (e.g., remove the variations in direct current). In some embodiments the RF coupler is not used, and the antenna is directly coupled (e.g., a diode) to the primary rectifier and the secondary rectifier. In such an embodiment, an input matching network may be placed between the antenna and the diode. In some embodiments, a wireless power receiver comprises a secondary rectifier configured to: (i) receive a second portion of the alternating current, and (ii) rectify the second portion of the alternating current into a secondary direct current having a second voltage and a second power level. In some embodiments, the direct current flows to a capacitor, and then flows to the ground. In some embodiments, the second power level of the secondary direct current is less than the first power level of the primary direct current. In some embodiments, the magnitude of the secondary direct current is a small amount of the received RF signals, either represented by a decibel value or a percentage of the incoming RF signals. For example, the power (i.e., voltage, or current) sent to the secondary rectifier can be −30 dB to −40 dB, or roughly less than 1% of the RF signals.

In some embodiments, the wireless power receiver's second voltage of the secondary direct current indicates whether the antenna is receiving RF signals from a wireless-power-transmitting device. In some embodiments, the magnitude of the secondary direct current can indicate that the secondary direct current is a minimum current necessary to indicate that the antenna is receiving the RF signals from the wireless-power-transmitting device, where the magnitude corresponds to a value of approximately −30 dB to −40 dB, or roughly 1% of the alternating current, or a voltage level of 1 volt to 40 volts. In some embodiments, the magnitude of the secondary direct current can be measured at multiple measurement points (e.g., at V_(AUX) 409-1 and V_(AUX_DIV) 409-2 in FIGS. 4A and 4E), and an amount of voltage detected at each of the measurement points can be controlled by using one or more resistors (fixed and/or variable). For example, as shown in FIGS. 4A and 4E, a voltage detected at V_(AUX) can be stepped down by using two in-series resistors, labelled as numerals 407 and 408. These measurement points (e.g., at V_(AUX) 409-1 and V_(AUX_DIV) 409-2 in FIGS. 4A and 4E) may be set depending on the type of detection mechanism. A few example detection mechanisms are: digital logic detection mechanism, voltage comparator detection mechanism, and/or an analog to direct current converter (ADC) detection mechanism.

When using a digital logic as a detection mechanism, the threshold voltage is set to half of the digital logic supply voltage (i.e. when supply voltage of digital logic is 5 volts, the logic threshold voltage can be set to be 2.5 volts). When the input is higher than the logic threshold voltage, the digital logic can output a “low” state that indicates that the input is lower than the logic threshold voltage. When the input voltage is lower than the logic threshold voltage, the digital logic can output a “high” state that indicates that the input is higher than the logic threshold voltage.

When using a voltage comparator as a detection mechanism, the threshold voltage can be set to any desired voltage within the supply range by using a voltage generator (i.e. the threshold voltage can be set to any value within supply voltage of the voltage comparator). When the input voltage is higher than the desired threshold voltage, the voltage comparator can output a “low” state that indicates that the input is lower than the desired threshold voltage. When the input voltage is lower than the desired threshold voltage, the voltage comparator can output a “high” state indicating that the input voltage is higher than desired threshold voltage.

When using analog to direct current converter (ADC), the threshold can be set arbitrarily using an external reference voltage. The ADC also digitizes the analog voltage value, which is used to tell how far apart the input voltage is from desired threshold (reference) voltage.

In some embodiments, the wireless power receiver includes an RF coupler that is coupled to the antenna, the RF coupler comprises distinct first and second outputs, and the primary rectifier is coupled to the first output of the RF coupler, while the secondary rectifier is coupled to the second output of the RF coupler.

In some embodiments, the wireless power receiver comprises at least one impedance matching network positioned between and coupled to the first output of the RF coupler and the secondary rectifier. In some embodiments, a series of matching networks may be implemented, as shown as 403-n in FIGS. 4B, 5B, and 6B. In some embodiments, the at least one matching network is configured to match an impedance of a source (e.g., a transmitter) of the RF signals.

In some embodiments, the wireless power receiver comprises at least one impedance matching network positioned between and coupled to an input of the RF coupler and the antenna, wherein the at least one matching network is configured to match an impedance of a source of the RF signals. In some embodiments, the wireless power receiver further comprises one or more additional electrical components (e.g., the one or more additional electrical components are capacitor 404, and Z_(L) 406, which represent the charging components the receiver is coupled to, as shown in FIGS. 4A, 4B, 4E, 6A, and 6B) that are used to deliver the primary direct current that is used to power or charge to the electronic device; and a controller configured to: detect that the second voltage of the secondary direct current satisfies one or more power-detection thresholds that indicate that the antenna is receiving RF signals from a wireless-power-transmitting device; and in response to detecting that the second direct current satisfies the one or more power-detection thresholds, send a signal that causes each of the one or more additional electrical components to prepare for receiving the primary direct current. In some embodiments the power-detection threshold is met when: (i) the voltage meets a value that corresponds to a received amount of the RF power signals (e.g., −40 dB to −1 dB), (ii) the voltage meets a value that corresponds to a percentage of the RF power signals (e.g., 0.001% to 2%), or (iii) the voltage is within a specified range (e.g., 1 volt to 40 volts, 5 volts to 30 volts, 5 volts to 10 volts).

In some embodiments, the one or more power-detection thresholds are satisfied when the second voltage of the secondary direct current is in a range of approximately 5 volts to 30 volts.

In some embodiments, detecting that the second voltage of the secondary direct current satisfies one or more power-detection thresholds is performed by comparing the second voltage to a respective power-detection threshold of the one or more power-detection thresholds at a first measurement point, a second measurement point, or both the first and second measurement points.

In some embodiments, the wireless power receiver comprises a first measurement point that is located before a voltage divider that is configured to step down the second voltage, and the second measurement point is located after the voltage divider. In some embodiments, variable resistors are used to adjust the resistance, and consequently adjust the voltage step down.

In some embodiments, the second portion of the alternating current is approximately 0.01% to 0.1% of the alternating current. And, in other embodiments, this range can be expanded or retracted, e.g., so that the range is from approximately 0.001% to 10%. In some other embodiments, the second portion of the alternating current range is expanded to cover approximately less than 1% of the alternating current. In some embodiments, the wireless power receiver comprises: (i) a first storage component (e.g., a first capacitor, or a battery) and (ii) a second storage component (e.g., a first capacitor, or a battery) having a lower storage capacity than the first storage component (e.g., a first capacitor, or a battery); the first storage component (e.g., a first capacitor, or a battery) is coupled to an output of the primary rectifier; the second storage component (e.g., a first capacitor, or a battery) is coupled to an output of the secondary rectifier; the second storage component (e.g., a first capacitor, or a battery), due to its lower storage capacity, is configured to discharge faster than the first storage component (e.g., a first capacitor, or a battery), wherein discharge of the second storage component (e.g., a first capacitor, or a battery) indicates to the wireless power receiver that RF signals are no longer being received at the antenna, and to prepare components of the wireless power receiver for shutdown.

In some embodiments, the secondary rectifier that is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode, and (iii) a second diode, and the input of the secondary rectifier is coupled to: a cathode of a first diode, wherein an anode of the first diode is coupled to a ground; and an anode of a second diode, wherein a cathode of the second diode is coupled to an output of the secondary rectifier. Although, this embodiment includes these components, it should be understood that other embodiments include these components in addition to other components.

In some embodiments, the secondary rectifier is composed of: (i) an input configured to receive the second portion of the alternating current, (ii) a first diode-connected transistor, and (iii) a second diode-connected transistor, and the input of the secondary rectifier is coupled to: (i) a first diode-connected transistor, wherein the first diode-connected transistor is connected to a ground; and (ii) a second diode-connected transistor, wherein the second diode-connected transistor is connected to an output of the secondary rectifier. Although, this embodiment includes these components, it should be understood that other embodiments include these components in addition to other components.

In some embodiments, the RF coupler is a directional coupler. In some embodiments, a directional coupler is a first path (e.g., a primary RF path) that is coupled to an antenna configured to receive RF signals and convert them to alternating current, and a second path (e.g., a secondary RF path) that is not coupled, but placed in parallel with the first path. In such an embodiment, the second path can be coupled to a resistor that is coupled to a ground.

In some embodiments, the RF coupler is a capacitive coupler. In some embodiments, a capacitive coupler includes an antenna coupled in parallel with a first capacitor, and a first path (e.g., a primary RF path). In such an embodiment, the first capacitor is coupled in parallel to a second capacitor, and a second path (e.g., a secondary RF path). In such embodiments, the second capacitor can be coupled to a ground.

In some embodiments, the RF coupler is a resistive coupler. In some embodiments, a resistive coupler includes an antenna coupled in parallel with a first resistor, and a first path (e.g., a primary RF path). In such an embodiment, the first resistor is coupled in parallel to a second resistor, and a second path (e.g., a secondary RF path). In such embodiments, the second resistor can be coupled to a ground.

In yet another aspect, the discussion below relates to power surge protection for a wireless power receiver. A method of power surge protection for a wireless power receiver, occurs at a wireless power receiver comprising: (i) an antenna, (ii) a rectifier coupled to the antenna, and (iii) a switch coupled to the rectifier, the switch configured to create an impedance mismatch or match before an input of the rectifier. While the switch is in a default-closed state that grounds the switch and creates an impedance mismatch before an input of the rectifier: receiving, by the antenna of the wireless power receiver, radio frequency (RF) signals as an alternating current, wherein a first portion of the alternating current is reflected away from the input of the rectifier due to the impedance mismatch, and a second portion of the alternating current flows through the switch and to ground; and while the switch is in an open state that creates an impedance match at the input of the rectifier: the first portion of the alternating current flows through the input of the rectifier, allowing the first portion of the alternating current to be converted into direct current that is used to charge or power an electronic device; and the second portion of the alternating current flows through the switch and to the input of the rectifier, allowing the second portion of the alternating current to be converted into direct current that is used to charge or power an electronic device. In this way, a switch can be employed to protect a sensitive component (e.g., rectifier) in a wireless-power-receiving circuit from initial surges of RF energy that may otherwise damage that sensitive component. In some embodiments, a capacitor may be placed between the antenna and the coupling mechanism. In some embodiments, an output of the rectifier is coupled to a capacitor that is coupled to a ground, which reduces ripple from the conversion of RF signals to direct current (DC) signals.

In some embodiments, a negative voltage generator is placed before the switch. In some embodiments, the negative voltage generator (i.e., a rectifier) rectifies RF signals to negative voltage, which causes the switch to enter an opened state by reaching a zero volt threshold.

In some embodiments, the switch transitions from the default-closed state to the open state gradually over a period of time, and during the period of time, a part of the first portion of the alternating current continues to be reflected away from the input of the rectifier. In some embodiments, over this period of time, the impedance mismatch gradually decreases, until the mismatch is substantially removed (e.g., less than 5% of the mismatch remains). In some embodiments, the period of time is determined by the specifications of the switch. In some embodiments, the switch may be a GaN switch or a depletion mode metal oxide semiconductor (MOS) switch that is designed to open after a set period of time. In some embodiments, the period of time can be dynamically adjusted based on a detected voltage of the alternating current.

In some embodiments, dynamically adjusting includes reducing the period of time based on a determination that the detected voltage does not satisfy (e.g., less than or equal to) a defined threshold value (e.g., the defined threshold can be between 4-10 volts, or another appropriate value that is slightly above a voltage used to charge a power source of the electronic device coupled to the wireless power receiver).

In some embodiments, dynamically adjusting includes increasing the period of time based on a determination that the detected voltage satisfies (e.g., is greater than) a defined threshold value.

In some embodiments, the switch transitions from default-closed to open state by using a Gallium Nitride (GaN) switch or a depletion mode metal oxide semiconductor (MOS) switch. In some embodiments, the switch has a voltage threshold that is met before it enters the open fully open. In some embodiments, the voltage threshold is zero volts.

In some embodiments, while the switch is in the open state: ceasing to receive the RF signals by the antenna of the wireless power receiver. The ceasing to receive the RF signals causes the switch to transition back to the default-closed state from the open state (e.g., when the voltage falls below a threshold voltages for the switch, as a result of no longer receiving the RF signals} {In some embodiments, the switch changes to the normally closed state when the voltage falls below a zero volt threshold).

In some embodiments, the wireless power receiver includes a coupling mechanism that is coupled to the antenna, wherein the coupling mechanism includes a first output and a second output, and further wherein: the first output of the coupling mechanism is coupled to the rectifier; and the second output of the coupling mechanism is coupled to the switch.

In some embodiments, the coupling mechanism partitions the alternating current, wherein the coupling mechanism: directs a first portion of the alternating current to the first output of the coupling mechanism; and directs a second portion of the alternating current to the second output of the coupling mechanism.

In some embodiments, the switch is coupled to an output of the rectifier. In some embodiments, the wireless power receiver further comprises a matching network having (i) an input coupled to the first output of the coupling mechanism and (ii) an output coupled to the rectifier. In some embodiments, more than one matching network may be utilized to match the impedance of the system to the source.

In some embodiments, the switch is coupled to the matching network and the rectifier. In some embodiments, the switch can be coupled to the output of a plurality of matching networks in a series.

Although some of various drawings illustrate a number of logical stages in a particular order, stages which are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art, so the ordering and groupings presented herein are not an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software, or any combination thereof.

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen in order to best explain the principles underlying the claims and their practical applications, to thereby enable others skilled in the art to best use the embodiments with various modifications as are suited to the particular uses contemplated. 

What is claimed is:
 1. A method of power surge protection for a wireless-power receiver, the method comprising: at a wireless-power receiver comprising: (i) an antenna, (ii) a rectifier coupled to the antenna, and (iii) a depletion-mode switch coupled to the rectifier, the depletion-mode switch being configured to create an impedance mismatch or an impedance match between the rectifier and the antenna: while the depletion-mode switch is in a default-closed state that creates the impedance mismatch between the rectifier and the antenna: receiving, by the antenna of the wireless-power receiver, radio frequency (RF) signals as an alternating current from a wireless power transmitter, wherein a first amount of the alternating current is reflected away from an input of the rectifier due to the impedance mismatch; while the impedance mismatch is present, providing a second amount of the alternating current to the depletion-mode switch to cause the depletion-mode switch to begin transitioning to an open state that creates the impedance match between the rectifier and the antenna; and while the depletion-mode switch is in the open state that creates the impedance match between the rectifier and the antenna: receiving, by the antenna of the wireless-power receiver, additional RF signals as an additional alternating current from the wireless power transmitter, wherein the additional alternating current flows through the input of the rectifier to be converted into direct current that is used to charge or power an electronic device.
 2. The method of claim 1 wherein a negative voltage generator is placed to drive the depletion-mode switch to transition from the default-closed state to the open state.
 3. The method of claim 1, wherein the depletion-mode switch transitions from the default-closed state to the open state gradually over a period of time, and during the period of time, a part of the first amount of the alternating current continues to be reflected away from the input of the rectifier.
 4. The method of claim 1, wherein the depletion-mode switch is a Gallium Nitride (GaN) switch or a metal oxide semiconductor (MOS) switch.
 5. The method of claim 1, wherein a period of time is required for the depletion-mode switch to transition to the open state, and the method further comprises, dynamically adjusting the period of time based on a detected voltage of the alternating current.
 6. The method of claim 5, wherein dynamically adjusting the period of time includes reducing the period of time based on a determination that the detected voltage does not satisfy a defined threshold value.
 7. The method of claim 5, wherein dynamically adjusting the period of time includes increasing the period of time based on a determination that the detected voltage satisfies a defined threshold value.
 8. The method of claim 1, wherein the depletion-mode switch has a voltage threshold that is met before it enters the open state.
 9. The method of claim 8, wherein the voltage threshold is zero volts.
 10. The method of claim 1, further comprising, while the depletion-mode switch is in the open state: ceasing to receive the RF signals by the antenna of the wireless-power receiver, wherein ceasing to receive the RF signals causes the depletion-mode switch to transition back to the default-closed state from the open state.
 11. The method of claim 1, wherein: the wireless-power receiver includes a coupling mechanism that is coupled to the antenna; the coupling mechanism includes a first output and a second output; the first output of the coupling mechanism is coupled to the rectifier; and the second output of the coupling mechanism is coupled to the depletion-mode switch.
 12. The method of claim 11, wherein the depletion-mode switch is coupled to an output of a second rectifier.
 13. A system for power surge protection for a wireless-power receiver, comprising: an antenna; a rectifier coupled to the antenna; a depletion-mode switch coupled to the rectifier, the depletion-mode switch being configured to create an impedance mismatch or an impedance match between the rectifier and the antenna; one or more processors; and memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for: while the depletion-mode switch is in a default-closed state that creates an impedance mismatch between the rectifier and the antenna: receiving, by the antenna of the wireless-power receiver, radio frequency (RF) signals as an alternating current from a wireless power transmitter, wherein a first amount of the alternating current is reflected away from an input of the rectifier due to the impedance mismatch; while the impedance mismatch is present, providing a second amount of the alternating current to the depletion-mode switch to cause the depletion-mode switch to begin transitioning to an open state that creates the impedance match between the rectifier and the antenna; and while the depletion-mode switch is in the open state that creates the impedance match between the rectifier and the antenna: receiving, by the antenna of the wireless-power receiver, additional RF signals as an additional alternating current from the wireless power transmitter, wherein the additional alternating current flows through the input of the rectifier to be converted into direct current that is used to charge or power an electronic device.
 14. The system of claim 13, further comprising a negative voltage generator configured to drive the depletion-mode switch to transition from the default-closed state to the open state.
 15. The system of claim 13, wherein the depletion-mode switch is configured to transition from the default-closed state to the open state gradually over a period of time, and during the period of time, a part of the first amount of the alternating current continues to be reflected away from the input of the rectifier.
 16. The system of claim 13, wherein a period of time is required for the depletion- mode switch to transition to the open state, and the period of time is configured to be dynamically adjusted based on a detected voltage of the alternating current.
 17. The system of claim 13, wherein: the depletion-mode switch has a voltage threshold that is met before it enters the open state; and the voltage threshold is zero volts.
 18. The system of claim 13, further comprising, while the depletion-mode switch is in the open state, the system is configured to: cease receiving RF signals by the antenna of the wireless-power receiver, wherein ceasing to receive the RF signals causes the depletion-mode switch to transition back to the default-closed state from the open state.
 19. The system of claim 13, wherein the depletion-mode switch is coupled to an output of a second rectifier.
 20. A non-transitory computer-readable storage medium storing one or more programs, the one or more programs comprising instructions, that when executed by a system with an antenna of a wireless-power receiver, a rectifier coupled to the antenna, and a depletion-mode switch coupled to the rectifier, the depletion-mode switch being configured to create an impedance mismatch or an impedance match between the rectifier and the antenna, cause the system to: while the depletion-mode switch is in a default-closed state that creates an impedance mismatch between the rectifier and the antenna: receive, by the antenna of the wireless-power receiver, radio frequency (RF) signals as an alternating current from a wireless power transmitter, wherein a first amount of the alternating current is reflected away from an input of the rectifier due to the impedance mismatch; while the impedance mismatch is present, provide a second amount of the alternating current to the depletion-mode switch to cause the depletion-mode switch to begin transitioning to an open state that creates the impedance match between the rectifier and the antenna; and while the depletion-mode switch is in the open state that creates the impedance match between the rectifier and the antenna: receive, by the antenna of the wireless-power receiver, additional RF signals as an additional alternating current from the wireless power transmitter, wherein the additional alternating current flows through the input of the rectifier to be converted into direct current that is used to charge or power an electronic device.
 21. The non-transitory computer-readable storage medium of claim 20, wherein the system that executes the instructions stored on the non-transitory computer-readable storage medium further comprises a negative voltage generator configured to drive the depletion-mode switch to transition from the default-closed state to the open state.
 22. The non-transitory computer-readable storage medium of claim 20, wherein the depletion-mode switch is configured to transition from the default-closed state to the open state gradually over a period of time, and during the period of time, a part of the first amount of the alternating current continues to be reflected away from the input of the rectifier.
 23. The non-transitory computer-readable storage medium of claim 20, wherein a period of time is required for the depletion-mode switch to transition to the open state, and the period of time is configured to be dynamically adjusted based on a detected voltage of the alternating current.
 24. The non-transitory computer-readable storage medium of claim 20, wherein: the depletion-mode switch has a voltage threshold that is met before it enters the open state; and the voltage threshold is zero volts.
 25. The non-transitory computer-readable storage medium of claim 20, further comprising instructions that, when executed by the system, cause the system to: while the depletion-mode switch is in the open state, cease receiving RF signals by the antenna of the wireless-power receiver, wherein ceasing to receive the RF signals causes the depletion-mode switch to transition back to the default-closed state from the open state.
 26. The non-transitory computer-readable storage medium of claim 20, wherein the depletion-mode switch is coupled to an output of a second rectifier. 